arm_mpam: resctrl: Fix the check for no monitor components found

arm_mpam: resctrl: Fix the check for no monitor components found

Dan Carpenter reports that, in mpam_resctrl_alloc_domain(), any_mon_comp is
used in an 'if' condition when it may be uninitialized. Initialize it to
NULL so that the check behaves correctly when no monitor components are
found.

Reported-by: Dan Carpenter <error27@gmail.com>
Fixes: 264c285999fc ("arm_mpam: resctrl: Add monitor initialisation and domain boilerplate")
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: James Morse <james.morse@arm.com>