spi: zynqmp_gqspi: do not round immediate_data field

spi: zynqmp_gqspi: do not round immediate_data field

Immediate_data is 8 bit value in generic FIFO command. When fields
data_xfer=1 and exponent=0 this field specifies the absolute number of data
bytes to read into the RXFIFO. Values from range 0xfd to 0xff are rounded
up to 0x100. It causes overwriting the next bit field which is data_xfer.
According to Zynq US+ TRM only DMA transfers should be word aligned. So
there is no reason to round up the immediate_data field.

Signed-off-by: Wojciech Tatarski <wtatarski@antmicro.com>
Signed-off-by: Tomasz Gorochowik <tgorochowik@antmicro.com>
Tested-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>