spi/topcliff_pch: Fix potential NULL dereference on allocation error

spi/topcliff_pch: Fix potential NULL dereference on allocation error

BugLink: https://bugs.launchpad.net/bugs/1863019
[ Upstream commit e902cdcb5112b89ee445588147964723fd69ffb4 ]

In pch_spi_handle_dma, it doesn't check for NULL returns of kcalloc
so it would result in an Oops.

Fixes: c37f3c2749b5 ("spi/topcliff_pch: DMA support")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>