MN10300: Fix interrupt mask alteration function call name in gdbstub

Fix the name of interrupt mask alteration function (ie the
local_change_intr_mask_level() fn) called in gdbstub to have an arch_
prefix to match the definition in asm/irqflags.h.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>