spi: atmel-quadspi: Add support for sama7g5 QSPI

The sama7g5 QSPI controller uses dedicated clocks for the
QSPI Controller Interface and the QSPI Controller Core, and
requires synchronization before accessing registers or bit
fields.

QSPI_SR.SYNCBSY must be zero before accessing any of the bits:
QSPI_CR.QSPIEN, QSPI_CR.QSPIDIS, QSPI_CR.SRFRSH, QSPI_CR.SWRST,
QSPI_CR.UPDCFG, QSPI_CR.STTFR, QSPI_CR.RTOUT, QSPI_CR.LASTXFER.

Also, the QSPI controller core configuration can be updated by
writing the QSPI_CR.UPDCFG bit to ‘1’. This is needed by the
following registers: QSPI_MR, QSPI_SCR, QSPI_IAR, QSPI_WICR,
QSPI_IFR, QSPI_RICR, QSPI_SMR, QSPI_SKR,QSPI_REFRESH, QSPI_WRACNT
QSPI_PCALCFG.

The Octal SPI supports frequencies up to 200 MHZ DDR. The need
for output impedance calibration arises. To avoid the degradation
of the signal quality, a PAD calibration cell is used to adjust
the output impedance to the driven I/Os.

The transmission flow requires different sequences for setting
the configuration and for the actual transfer, than what is in
the sama5d2 and sam9x60 versions of the IP. Different interrupts
are handled. aq->ops->set_cfg() and aq->ops->transfer() are
introduced to help differentiating the flows.

Tested single and octal SPI mode with mx66lm1g45g.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20211214133404.121739-1-tudor.ambarus@microchip.com

Author: ambarus