ARM: cache-l2x0.c: consistently use u32

__u32 exists to avoid namespace clashes with userspace programs.  It
should not be used outside header files, so convert to use u32 instead.
Also, don't mix uint32_t and __u32 - use the same type throughout the
file for consistency.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>