staging: lustre: simplify ptlrpc_deactivate_and_unlock_import

The locking scheme used in ptlrpc_deactivate_and_unlock_import and
ptlrpc_deactivate_import generates the followings sparse errors:
drivers/staging/lustre/lustre/ptlrpc/import.c:209:9: warning: context
imbalance in 'ptlrpc_deactivate_and_unlock_import' - unexpected unlock
drivers/staging/lustre/lustre/ptlrpc/import.c:221:6: warning: context
imbalance in 'ptlrpc_deactivate_import' - wrong count at exit

As ptlrpc_deactivate_and_unlock_import is only used by
ptlrpc_deactivate_import as a helper function, this patch moves its code
into ptlrpc_deactivatre_import to fix the sparse warnings.

Signed-off-by: Maxime Lorrillere <maxime.lorrillere@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>