[ARM] Fix freeing of page tables for ARM in free_pgd_slow

Since 2f569afd

 (CONFIG_HIGHPTE vs. sub-page page tables.) pte_free() calls
pte_lock_deinit() and dec_zone_page_state().  So free_pgd_slow must not call
the latter two when calling the first.

Signed-off-by: Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>