arm: fix v[78]-r multilibs when configured with --with-multlib-list=aprofile

arm: fix v[78]-r multilibs when configured with --with-multlib-list=aprofile

When gcc for Arm is configured with --with-multilib-list=aprofile a
misplaced endif directive in the makefile was causing the arm->thumb
mapping for multilibs to be omitted from the reuse rules.  This
resulted in the default multilib being picked rather than the thumb2
opimized version.

	* config/arm/t-multilib: Use arm->thumb multilib reuse rules
	on a-profile.

From-SVN: r279128