defconfig: msm: Enable serial console driver for SA2150P perf

Enable the serial console driver even for the perf
variant of SA2150P. This is to enable a development
shell for convenience.

Change-Id: Icc63ca8c583edb9bcc8772318f221ee9629688ac
Signed-off-by: Gustavo Solaira <gustavos@codeaurora.org>