Fix SPI register masking in busWriteBuf

Correct the SPI register address masking in busWriteBuf() to clear the
MSB instead of setting it. For SPI protocol, the MSB indicates read (1)
or write (0) operations. Write operations should use (reg & 0x7F) to
clear the MSB, not (reg | 0x80) which sets it.

This matches the correct implementation in busWrite() at line 318 which
uses (reg & 0x7F) for write operations.

Note: This bug affects theoretical future SPI devices using buffer writes.
Current devices using busWriteBuf() are all I2C-based (VL53L0X, VL53L1X,
MLX90393, TERARANGER_EVO, US42 rangefinders) and are unaffected.

Fixes #10674

Author: sensei-hacker

src/main/drivers/bus.c

@@ -283,7 +283,7 @@ bool busWriteBuf(const busDevice_t * dev, uint8_t reg, const uint8_t * data, uin
                 return spiBusWriteBuffer(dev, reg, data, length);
             }
             else {
-                return spiBusWriteBuffer(dev, reg | 0x80, data, length);
+                return spiBusWriteBuffer(dev, reg & 0x7F, data, length);
             }
 #else
             return false;