arch: arm: aarch32: Fix spurious interrupt handling

The GIC can return 0x3ff to indicate a spurious interrupt.  Other
interrupt controllers could return something different.  Check that the
pending interrupt is valid in order to avoid indexing past the end of
the isr_table.

This fixes #30465 and is based on the aarch64 fix in 9dd2731d.

Signed-off-by: Bradley Bolen <bbolen@lexmark.com>