perf: use PACKAGECONFIG instead of hand-rolled logic
PERF_FEATURES_ENABLE and perf_feature_enabled() was basically a poor man's clone
of PACKAGECONFIG, without the automatic handling of dependencies and configure
options.
As part of the port to PACKAGECONFIG the options have been changed to remove the
perf- prefix, but are otherwise unchanged.
Also remove BUILDPERF_libc_uclibc assignment as nothing in the metadata uses a
BUILDPERF variable.
Signed-off-by: Ross Burton <ross.burton@intel.com>
