drm/i915/dsb: Use intel_dsb_ins_align() in intel_dsb_align_tail()

If the free_post is not QW aligned we don't have to memset the
extra DW needed to make it so, as the only way that can happen
is via intel_dsb_reg_write_indexed() which already makes sure
the next DW is zeroed.

Not a big deal, but this is more consistent how all the other
stuff operates that puts instructions into the DSB buffer, and
we'll get a few more of those soon.

Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250612145018.8735-2-ville.syrjala@linux.intel.com

Author: vsyrjala

drivers/gpu/drm/i915/display/intel_dsb.c

@@ -527,6 +527,8 @@ static void intel_dsb_align_tail(struct intel_dsb *dsb)
 {
 	u32 aligned_tail, tail;
 
+	intel_dsb_ins_align(dsb);
+
 	tail = dsb->free_pos * 4;
 	aligned_tail = ALIGN(tail, CACHELINE_BYTES);