Revert "Fix data race between zil_commit() and zil_suspend()"

This reverts commit 4c856fb333 to
resolve a newly introduced deadlock which in practice in more
disruptive that the issue this commit intended to address.

Reviewed-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Reviewed-by: Mark Maybee <mark.maybee@delphix.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #14775
Closes #14790

include/sys/zil_impl.h

@@ -183,7 +183,6 @@ struct zilog {
 	uint64_t	zl_destroy_txg;	/* txg of last zil_destroy() */
 	uint64_t	zl_replayed_seq[TXG_SIZE]; /* last replayed rec seq */
 	uint64_t	zl_replaying_seq; /* current replay seq number */
-	krwlock_t	zl_suspend_lock;	/* protects suspend count */
 	uint32_t	zl_suspend;	/* log suspend count */
 	kcondvar_t	zl_cv_suspend;	/* log suspend completion */
 	uint8_t		zl_suspending;	/* log is currently suspending */