ARM: l2c: avoid calling outer_flush_all() unnecessarily (Spear)

Spear calls outer_flush_all() from it's SMP bringup function.  This
is potentially dangerous as the L2C set/way operations which implement
this don't take kindly to concurrent operations.  Besides, there's
better solutions to this, as implemented on other platforms.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>