defconfig: 8084: Set ROW as the default block I/O scheduler

The ROW block I/O scheduler was developed with the mobile devices needs
in mind, where we favor user experience upon everything else, thus we
want to give READ I/O requests as much priority as possible.

The main idea of the ROW scheduling policy is to dispatch READ requests
with higher priority, while write starvation is considered.

The benefit of ROW block I/O scheduler is to improve the READ throughput
and latency in READ/WRITE collisions.
The READ latency worst case is improved both in sequential and random read
scenarios.
The apq8084_defconfig already has this configuration -
update apq8084-perf_defconfig to match

Change-Id: I988c89111747883c6de67ac9a78123ce7cf2c5ae
Signed-off-by: Yaniv Gardi <ygardi@codeaurora.org>