defconfig: enable RCU_FAST_NO_HZ for SMP msm targets

RCU_FAST_NO_HZ has been shown to improve power consumption
thanks to CPUs entering nohz idle mode more quickly.

The 7627a and 8660 configurations are omitted until they
can be properly tested with RCU_FAST_NO_HZ.

From https://www.codeaurora.org/gitweb/quic/la/?p=kernel/msm.git;a=commit;h=df997664f786b514cce239fa51b370a01925ce1e

Change-Id: Idf9613ed0deb808d0d45c5bd76385c686574365f