Support gdb.asm/asm-source.exp on powerpc64le

Add new powerpc64le.inc file appropriate for the ELFv2 ABI and
use it to support the asm-source.exp test case on powerpc64le.

gdb/testsuite/
2014-03-25  Ulrich Weigand  <uweigand@de.ibm.com>

	* gdb.asm/asm-source.exp: Handle powerpc64le-* targets.
	* gdb.asm/powerpc64le.inc: New file.