[Arm] Fix multilibs for Armv7-R

[Arm] Fix multilibs for Armv7-R

This patch maps multilibs using -march=armv7-r+vfpv3-d16-fp16 and
-march=armv7-r+vfpv3-d16-fp16+idiv to v7+fp.  This patch also adds a new
multilib for armv7-r+fp.sp and maps -march=armv7-r+fp.sp+idiv,
-march=armv7-r+vfpv3xd-fp16 and -march=armv7-r+vfpv3xd-fp16+idiv to it.

This patch also makes it so that the generated multilib header file is
regenerated if changes have been made to either t-multilib, t-aprofile or
t-rmprofile when doing incremental builds.

gcc/ChangeLog:
2019-10-18  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* config/arm/t-multilib: Add rule to regenerate mutlilib header file
	with any change to t-multilib, t-aprofile and t-rmprofile.  Also add
	new multilib variants and new mappings.

gcc/testsuite/ChangeLog:
2019-10-18  Andre Vieira  <andre.simoesdiasvieira@arm.com>

	* gcc.target/arm/multilib.exp: Add extra tests.

From-SVN: r277156