ARM: 9054/1: arch/arm/mm/mmu.c: Remove duplicate header

Remove asm/fixmap.h which is included more than once.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Hailong Liu <liu.hailong6@zte.com.cn>
Signed-off-by: Hailong Liu <carver4lio@163.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>