drivers: espi: espi_mchp_xec: Fix wrong size type for status var

In status variable in espi_pc_isr should have been a 32-bit unsigned int
as ESPI_PC_REGS->PC_STATUS is 32-bits.

Fixes #18359
Coverity-CID: 203521

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>