defconfig: 8974: Disable MSM8226 support in perf defconfig as well

The MSM8974 and MSM8226 targets are not sufficiently compatible to
be supported in a single-binary kernel configuration. It was
disabled already in normal defconfig and following the same for
perf defconfig.

Change-Id: I6c8dd6f7f3c287e644e1a18077111a276092c33e
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>