drivers: serial: uart: ns16550 add missing isr locking

The existing uart driver ns16550 did not have ISR locking that
effected IO APIC working in fixed delivery mode in SMP system
x86_64. This commit adds ISR locking mechanism using spinlock
for the interrupt related services.

The CONFIG_IPM_CONSOLE_STACK_SIZE is increased to lift
limitation of stack size experienced in IPM driver test with
this spinlock impelentation.

Fixes #23026

Signed-off-by: Jennifer Williams <jennifer.m.williams@intel.com>