powerpc: Wire up memtest

Add call to early_memtest() so that kernel compiled with
CONFIG_MEMTEST really perform memtest at startup when requested
via 'memtest' boot parameter.
Tested-by: NDaniel Axtens <dja@axtens.net>
Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

Documentation/admin-guide/kernel-parameters.txt

@@ -2404,7 +2404,7 @@
 			seconds.  Use this parameter to check at some
 			other rate.  0 disables periodic checking.
 
-	memtest=	[KNL,X86,ARM] Enable memtest
+	memtest=	[KNL,X86,ARM,PPC] Enable memtest
 			Format: <integer>
 			default : 0 <disable>
 			Specifies the number of memtest passes to be

arch/powerpc/kernel/setup-common.c

@@ -33,6 +33,7 @@
 #include <linux/serial_8250.h>
 #include <linux/percpu.h>
 #include <linux/memblock.h>
+#include <linux/bootmem.h>
 #include <linux/of_platform.h>
 #include <linux/hugetlb.h>
 #include <asm/debugfs.h>
@@ -966,6 +967,8 @@ void __init setup_arch(char **cmdline_p)
 
 	initmem_init();
 
+	early_memtest(min_low_pfn << PAGE_SHIFT, max_low_pfn << PAGE_SHIFT);
+
 #ifdef CONFIG_DUMMY_CONSOLE
 	conswitchp = &dummy_con;
 #endif