RMX1921: Remove IO read_ahead_kb tune

If we set 2048KB ra value in the beginning of the
boot process, services initialized at this time
would keep 2048KB ra value even though we adjust the
ra value
to 128KB after boot completion.

This may cause memory pressure.

Bug: 174700194
Signed-off-by: Randall Huang <huangrandall@google.com>
Change-Id: I97ee0ee9511eaada011f2634afd68d68cdca4570
Signed-off-by: kaderbava <ksbava7325@gmail.com>