arm64: mte: fix prctl(PR_GET_TAGGED_ADDR_CTRL) if TCF0=NONE

arm64: mte: fix prctl(PR_GET_TAGGED_ADDR_CTRL) if TCF0=NONE

Previously we were always returning a tag inclusion mask of zero via
PR_GET_TAGGED_ADDR_CTRL if TCF0 was set to NONE. Fix it by making
the code for the NONE case match the others.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Iefbea66cf7d2b4c80b82f9639b9ea7f33f7fac53
Fixes: af5ce95282dc ("arm64: mte: Allow user control of the generated random tags via prctl()")
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20201203075110.2781021-1-pcc@google.com
Signed-off-by: Will Deacon <will@kernel.org>