spi: cadence_qspi: Address the comparison failure for 0-8 bytes of data

The current implementation encounters issues when testing data ranging
from 0 to 8 bytes. This was confirmed through testing with both ISSI
(IS25WX256) and Micron (MT35XU02G) Flash exclusively in SDR mode.

Upon investigation, it was observed that utilizing the
"SPI_NOR_OCTAL_READ" flag and attempting to read less than 8 bytes in
STIG mode results in a read failure, leading to a compare test failure.

To resolve this issue, the CMD_4BYTE_FAST_READ opcode is now utilized
instead of CMD_4BYTE_OCTAL_READ, specifically in SDR mode.

This is based on patch series:
https://lore.kernel.org/all/cover.1701853668.git.tejas.arvind.bhumkar@amd.com/



Signed-off-by: Tejas Bhumkar <tejas.arvind.bhumkar@amd.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>