intel/fs: Fix a typo in need_matching_subreg_offset

This fixes a bunch of Vulkan subgroup tests on little core platforms.

Fixes: 4150920b "intel/fs: Add a helper for emitting scan operations"
Reviewed-by: Caio Marcelo de Oliveira Filho <caio.oliveira@intel.com>
Tested-by: Mark Janes <mark.a.janes@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
(cherry picked from commit 7e7959fc)