simpleperf: fix dumping arm regs.

In perf.data recorded for 32-bit processes on arm64, the register
data contains both arm registers and arm64 registers. So GetRegName()
needs to support arm64 registers when arch == ARCH_ARM.

Also remove an unneeded warning in dump cmd.

Bug: none
Test: run simpleperf_unit_test
Change-Id: I2c73a422f2965efd1686fec62a8b6ddd43fa2687
4 files changed