Use ARM software breakpoint for target of 'bx pc'

thumb_get_next_pc_raw():
The 'bx pc' and 'blx pc' instructions will necessarily take ARM
CPUs out of Thumb mode, because the pc register's value can never
be odd.

See https://code.google.com/p/android/issues/detail?id=56962



Signed-off-by: Ryan V. Bissell <rbissell@nvidia.com>