Create um_flags in the ufsmount structure to hold flags for a UFS filesystem.

Create um_flags in the ufsmount structure to hold flags for a UFS filesystem.
Convert integer structure flags to use um_flags:

	int	um_candelete;			/* devvp supports TRIM */
	int	um_writesuspended;		/* suspension in progress */

become:

#define UM_CANDELETE		0x00000001	/* devvp supports TRIM */
#define UM_WRITESUSPENDED	0x00000002	/* suspension in progress */

This is in preparation for adding other flags to indicate forcible
unmount in progress after a disk failure and possibly forcible
downgrade to read-only.

No functional change intended.

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