Fix IP register usage in LoadClassSlowPathARMVIXL.

Request a temporary from a UseScratchRegisterScope instead
of explicitly specifying the IP register to avoid assetion
failure in VIXL.

Test: Build aosp_flounder-userdebug with ART_USE_VIXL_ARM_BACKEND=true
Bug: 34340177
Bug: 30627598
Change-Id: Ie39fbbb66165d752634cde8d2963129641558b93
1 file changed