drivers:spi:cadence-xspi: Add low-level changes to support kmsg panic/oops write

commit 214607e05d26da004977e7836f1a53b925f3ad01 from
git@git.assembla.com:cavium/WindRiver.linux.git

Enable handling of panic and oops logs through pstore mechanism for
Cadence-xspi. Work is derived from existing code from Bhaskara
Budiredla. Original commit message is attached below.

drivers:spi:cadence-xspi: Add low-level changes to support kmsg panic/oops write

To enable the writing of panic and oops logs, Cadence specific
spi-nor master driver changes are made to ensure the functioning of mtdpstore.

Signed-off-by: Bhaskara Budiredla <bbudiredla@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/64285
Reviewed-by: Witold Sadowski <wsadowski@marvell.com>
Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Tested-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>

Change-Id: I2c0638d069439b78c870f4e4fed71e11e779844c
Signed-off-by: Witold Sadowski <wsadowski@marvell.com>
Signed-off-by: Wojciech Bartczak <wbartczak@marvell.com>
Reviewed-on: https://sj1git1.cavium.com/c/IP/SW/kernel/linux/+/67436
Reviewed-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Tested-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>