tests: remove duplicate name for the kernel arch.interrupt test

After SanityCheck I found out, that test arch.interrupt
still has same duplicate names.
To get rid of it, I decided to change the duplicate test case name in
arch/arm/arm_interrupt to arch.interrupt.arm since that is not
a generic interrupt test but is ARM-specific.

Signed-off-by: Maksim Masalski <maksim.masalski@intel.com>