The L310_PREFETCH_CTRL register bits 28 and 29 to enable data and
instruction prefetch respectively can also be accessed via the
L2X0_AUX_CTRL register.  They appear to be actually wired together in
hardware between the registers.  Changing them in the prefetch
register only will get undone when restoring the aux control register
later on.  For this reason, set these bits in both registers during
initialisation according to the devicetree property values.

Link: https://lore.kernel.org/lkml/76f2f3ad5e77e356e0a5b99ceee1e774a2842c25.1597061474.git.guillaume.tucker@collabora.com/

Fixes: ec3bd0e6 ("ARM: 8391/1: l2c: add options to overwrite prefetching behavior")
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>