arm, vt8500, LLVMLlinux: Use mcr instead of mcr% for mach-vt8500

The ASM below does not compile with clang and is not the way that the mcr
command is used in other parts of the kernel.

arch/arm/mach-vt8500/vt8500.c:72:11: error: invalid % escape in inline assembly string
        asm("mcr%? p15, 0, %0, c7, c0, 4" : : "r" (0));
            ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.

There are other forms that are supported on different ARM instruction sets but
generally the kernel just uses mcr as it is supported in all ARM instruction
sets.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Mark Charlebois <charlebm@gmail.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Tony Prisk <linux@prisktech.co.nz>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>