The Broadcom Brahma-B15 CPU readahead cache registers will be restored
to their Power-on-Reset values after a S3 suspend/resume cycles, so we
want to restore what we had enabled before.

Another thing we want to take care of is disabling the read-ahead cache
prior to suspending to avoid any sort of side effect with the spinlock
we need to grab to serialize register accesses.
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>