lockdep, rwsem: fix down_write_nest_lock() if !CONFIG_DEBUG_LOCK_ALLOC

Commit ("lockdep, rwsem: provide down_write_nest_lock()")
contains a bug
in a codepath when CONFIG_DEBUG_LOCK_ALLOC is disabled,
which causes
down_read() to be called instead of down_write() by mistake
on such
configurations.  Fix that.

Change-Id:
I1b463f6df91cf12e6c23f3fa751cdbd315d07f88
Reported-and-tested-by: Andrew
Clayton <andrew@digital-domain.net>
Reported-and-tested-by: Zlatko
Calusic <zlatko.calusic@iskon.hr>
Signed-off-by: Jiri Kosina
<jkosina@suse.cz>
Reviewed-by: Rik van Riel
<riel@redhat.com>
Signed-off-by: Linus Torvalds
<torvalds@linux-foundation.org>

idea is taken here -
https://github.com/jrior001/android_kernel_samsung_d2/commit/d93c41d9563164cf1197b3d4077e9b2feb170e90