[ARM] remove unused #include <version.h>

The driver(s) below do not use LINUX_VERSION_CODE nor KERNEL_VERSION.
  arch/arm/plat-mxc/clock.c

This patch removes the said #include <version.h>.

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>