vt: selection, fix double lock introduced by a merge

The merge commit cb05c6c8 (Merge 5.6-rc5 into tty-next) introduced a
double lock to set_selection_kernel. vc_sel.lock is locked both in
set_selection_kernel and its callee __set_selection_kernel now.

Remove the latter.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lore.kernel.org/r/20200316064544.4799-1-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>