ARM: dts: at91: sam9x60ek: Disable slewrate to fix performance on NAND

NAND pins have switching frequency above 50Mhz, slewrate must be disabled.

With this, the performance is improved from:
mtd_speedtest: page write speed is 5845 KiB/s
mtd_speedtest: page read speed is 7538 KiB/s
to:
mtd_speedtest: page write speed is 9814 KiB/s
mtd_speedtest: page read speed is 18123 KiB/s

Fixes: f724cf5 ("pinctrl: at91: Enable slewrate by default on SAM9X60")
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>

Author: ambarus

arch/arm/boot/dts/at91-sam9x60ek.dts

@@ -465,8 +465,8 @@
 				nand {
 					pinctrl_nand_oe_we: nand-oe-we-0 {
 						atmel,pins =
-							<AT91_PIOD 0 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 1 AT91_PERIPH_A AT91_PINCTRL_NONE>;
+							<AT91_PIOD 0 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 1 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)>;
 					};
 
 					pinctrl_nand_rb: nand-rb-0 {
@@ -483,14 +483,14 @@
 				ebi {
 					pinctrl_ebi_data_0_7: ebi-data-lsb-0 {
 						atmel,pins =
-							<AT91_PIOD 6 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 7 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 8 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 9 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 10 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 11 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 12 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 13 AT91_PERIPH_A AT91_PINCTRL_NONE>;
+							<AT91_PIOD 6 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 7 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 8 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 9 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 10 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 11 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 12 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 13 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)>;
 					};
 
 					pinctrl_ebi_data_0_15: ebi-data-msb-0 {
@@ -515,8 +515,8 @@
 
 					pinctrl_ebi_addr_nand: ebi-addr-0 {
 						atmel,pins =
-							<AT91_PIOD 2 AT91_PERIPH_A AT91_PINCTRL_NONE
-							 AT91_PIOD 3 AT91_PERIPH_A AT91_PINCTRL_NONE>;
+							<AT91_PIOD 2 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)
+							 AT91_PIOD 3 AT91_PERIPH_A (AT91_PINCTRL_NONE | AT91_PINCTRL_SLEWRATE_DIS)>;
 					};
 				};