efi/arm64: Fix kmemleak false positive in arm64_efi_rt_init()

The kmemleak code sometimes complains about the following leak:

unreferenced object 0xffff8000102e0000 (size 32768):
  comm "swapper/0", pid 1, jiffies 4294937323 (age 71.240s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000db9a88a3>] __vmalloc_node_range+0x324/0x450
    [<00000000ff8903a4>] __vmalloc_node+0x90/0xd0
    [<000000001a06634f>] arm64_efi_rt_init+0x64/0xdc
    [<0000000007826a8d>] do_one_initcall+0x178/0xac0
    [<0000000054a87017>] do_initcalls+0x190/0x1d0
    [<00000000308092d0>] kernel_init_freeable+0x2c0/0x2f0
    [<000000003e7b99e0>] kernel_init+0x28/0x14c
    [<000000002246af5b>] ret_from_fork+0x10/0x20

The memory object in this case is for efi_rt_stack_top and is allocated
in an initcall. So this is certainly a false positive. Mark the object
as not a leak to quash it.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

arch/arm64/kernel/efi.c

@@ -9,6 +9,7 @@
 
 #include <linux/efi.h>
 #include <linux/init.h>
+#include <linux/kmemleak.h>
 #include <linux/screen_info.h>
 #include <linux/vmalloc.h>
 
@@ -213,6 +214,7 @@ l:	if (!p) {
 		return -ENOMEM;
 	}
 
+	kmemleak_not_leak(p);
 	efi_rt_stack_top = p + THREAD_SIZE;
 	return 0;
 }