arm: mvebu: Don't disable cache at startup on Armada XP at all

This patch leaces the cache configuration untouched for the AXP in the
setup done by the BootROM. Resulting in the cache still being enabled
at the startup of U-Boot. This leads to a slightly faster boot to the
U-Boot prompt (or Linux of course).

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>