ART: Print short register names with MIPS64

MIPS64 back-end would print register names as "GpuRegister: X" or
"FpuRegister: X". Space separates Checker attributes and therefore
caused a test to fail. This patch changes it to print "aX" and "fX"
respectively.

Change-Id: Iffae989f25563ef074dd7ef0b09cdfe438119cee
1 file changed