arm64: add support for memtest

Add support for memtest command line option.
Signed-off-by: NVladimir Murzin <vladimir.murzin@arm.com>
Acked-by: NWill Deacon <will.deacon@arm.com>
Tested-by: NMark Rutland <mark.rutland@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/arm64/mm/init.c

@@ -190,6 +190,8 @@ void __init bootmem_init(void)
 	min = PFN_UP(memblock_start_of_DRAM());
 	max = PFN_DOWN(memblock_end_of_DRAM());
 
+	early_memtest(min << PAGE_SHIFT, max << PAGE_SHIFT);
+
 	/*
 	 * Sparsemem tries to allocate bootmem in memory_present(), so must be
 	 * done after the fixed reservations.