spi: spi_amd: Optimize IO operations

spi: spi_amd: Optimize IO operations

Read and write the maximum number of data bytes at once, rather than byte
by byte. This improves AMD SPI controller driver performance by reducing
the time required to access FIFO registers. For example, with the new
changes, 64 bytes of data from the FIFO queue can be read in 8 read calls
(8 bytes per call) instead of 64 read calls(1 byte per call).

Co-developed-by: Krishnamoorthi M <krishnamoorthi.m@amd.com>
Signed-off-by: Krishnamoorthi M <krishnamoorthi.m@amd.com>
Co-developed-by: Akshata MukundShetty <akshata.mukundshetty@amd.com>
Signed-off-by: Akshata MukundShetty <akshata.mukundshetty@amd.com>
Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
Link: https://patch.msgid.link/20240925133644.2922359-6-Raju.Rangoju@amd.com
Signed-off-by: Mark Brown <broonie@kernel.org>