[ARM] 3362/1: [cleanup] - duplicate decleration of mem_fclk_21285

Patch from Ben Dooks

arch/arm/kernel/setup.c declares mem_fclk_21285 when
this is already declared in include/asm-arm/system.h

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