FROMGIT: arm64: fix warning in mte_get_random_tag()

The simplification of mte_get_random_tag() caused the introduction of the
warning below:

In file included from arch/arm64/include/asm/kasan.h:9,
                 from include/linux/kasan.h:16,
                 from mm/kasan/common.c:14:
mm/kasan/common.c: In function `mte_get_random_tag':
arch/arm64/include/asm/mte-kasan.h:45:9: warning: `addr' is used
                                         uninitialized [-Wuninitialized]
   45 |         asm(__MTE_PREAMBLE "irg %0, %0"
      |

Fix the warning using "=r" for the address in the asm inline.

Link: https://lkml.kernel.org/r/20210211152208.23811-1-vincenzo.frascino@arm.com


Fixes: c8f8de4c0887 ("arm64: kasan: simplify and inline MTE functions")
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Acked-by: Andrey Konovalov <andreyknvl@google.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
(cherry picked from commit 37a7f3b88e3dde2479e1aa93847093b5e97a9c01
 https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git akpm)
Bug: 172318110
Change-Id: I7c52f84b9d746373c341a7cd36b12309ab993141