package/linux-tools/perf: bear the kernel options munging

perf by itself is not a standalone package; instead, it is part of a
bigger package, linux-tools.

Even though perf is the only one to need kernel .config fixups, we still
do it in a generic way, as it blends nicely in the existing variables,
which all use a loop over all the tools.

Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>