spi: spi-mem: Claim SPI bus before spi mem access

spi: spi-mem: Claim SPI bus before spi mem access

It is necessary to call spi_claim_bus() before starting any SPI
transactions and this restriction would also apply when calling spi-mem
operations. Therefore claim and release bus before requesting transfer
via exec_op.

Signed-off-by: Vignesh R <[email protected]>
Tested-by: Simon Goldschmidt <[email protected]>
Tested-by: Stefan Roese <[email protected]>
Tested-by: Horatiu Vultur <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>
Tested-by: Jagan Teki <[email protected]> #zynq-microzed