spi: spi-cadence: Update ISR status variable type to irqreturn_t

Data type of status variable, that hold the return value of the ISR,
should be irqreturn_t & not u32. This patch updates status variable type
to irqreturn_t.

Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xilinx.com>
Link: https://lore.kernel.org/r/20220512145025.20205-1-amit.kumar-mahapatra@xilinx.com
Signed-off-by: Mark Brown <broonie@kernel.org>