LU-14628 ptlrpc: remove might_sleep() in sptlrpc_gc_del_sec()

LU-14628 ptlrpc: remove might_sleep() in sptlrpc_gc_del_sec()

sptlrpc_gc_del_sec() calls mutex_lock() which calls might_sleep(), so
the explicit might_sleep() call can be removed as redundant.

Signed-off-by: Nikitas Angelinas <nikitas.angelinas@hpe.com>
Test-Parameters: trivial
Change-Id: I48714fae12e63ba5e37ec0f9aa3ab7f688b9475d
Reviewed-on: https://review.whamcloud.com/43397
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>