arm: perf: clean up PMU names

The perf userspace tools can't handle dashes or spaces in PMU names,
which conflicts with the current naming scheme in the arm perf backend.
This prevents these PMUs from being accessed by name from the perf
tools. Additionally the ARMv6 pmus are named "v6", which does not fully
distinguish them in the sys/bus/event_source namespace.

This patch renames the PMUs consistently to a lower case form with
underscores, e.g. "armv6_1176", "armv7_cortex_a9". This is both readily
accepted by today's perf tool, and far easier to type than the
(apparently unused) convention in use previously. The OProfile name
conversion code is updated to handle this.

Due to a copy-paste error involving two "xscale1" entries, "xscale2" has
never been matched by the name OProfile name mapping. While we're
updating names, this is corrected.

Acked-by: Will Deacon <will.deacon@arm.com>
Tested-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
[sachin: fixed missing semicolons in armv6 backend]
Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>