ANDROID: gki_defconfig: enable CONFIG_BLK_CGROUP_IOPRIO

Using cgroup to adjust the io priority can make the process
with high io priority respond faster, so enable the config
to avoid some key processes from being unresponsive under
the condition of high io pressure.

When writing files directly under a certain load, files with
high io priority will be completed faster:
The write rate of a file whose io priority policy is none is 2.3MB/s
The write rate of a file whose io priority policy is none-to-rt is 3.5MB/s

Bug: 271937162
Change-Id: I387ac4792c89d88d131c5146b116a0393c01b096
Signed-off-by: Cixi Geng <cixi.geng1@unisoc.com>