arm64: signal32: Drop pointless call to sigdelsetmask()

arm64: signal32: Drop pointless call to sigdelsetmask()

Commit 3c41aa3cd26a ("most of set_current_blocked() callers want
SIGKILL/SIGSTOP removed from set") extended set_current_blocked() to
remove SIGKILL and SIGSTOP from the new signal set and updated all
callers accordingly.

Unfortunately, this collided with the merge of the arm64 architecture,
which duly removes these signals when restoring the compat sigframe, as
this was what was previously done by arch/arm/.

Remove the redundant call to sigdelsetmask() from
compat_restore_sigframe().

Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210825093911.24493-1-will@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>