uprobes: Kill uprobe_events, use RB_EMPTY_ROOT() instead
uprobes: Kill uprobe_events, use RB_EMPTY_ROOT() instead

uprobe_events counts the number of uprobes in uprobes_tree but
it is used as a boolean. We can use RB_EMPTY_ROOT() instead.

Probably no_uprobe_events() added by this patch can have more
callers, say, mmf_recalc_uprobes().

Signed-off-by: Oleg Nesterov <20b70f0af00562e63758b9ee42012ecc96c58590@redhat.com>
Acked-by: Anton Arapov <14deb5e5e417133e888bf47bb6a3555c9bb7d81c@redhat.com>
Acked-by: Srikar Dronamraju <1f69195f6d934d4caf5816234bde319316df237e@linux.vnet.ibm.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs