ARM: 5912/1: Define a 32-bit Thumb-2 breakpoint instruction

Recognize 0xf7f0 0xa000 as a 32-bit breakpoint instruction for
Thumb-2.

Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>