meson: Cleanup usage dri_drivers as it's a dead option

Initial value of with_dri have no relation with dri_drivers.length()
Do not show useless `DRI drivers:`

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17821>

meson.build

@@ -180,8 +180,6 @@ if dri_drivers.length() != 0
   error('Mesa\'s main branch no longer has any "classic" drivers, use the "amber" branch instead.')
 endif
 
-with_dri = dri_drivers.length() != 0
-
 gallium_drivers = get_option('gallium-drivers')
 if gallium_drivers.contains('auto')
   if system_has_kms_drm
@@ -238,6 +236,7 @@ endforeach
 with_gallium = gallium_drivers.length() != 0
 with_gallium_kmsro = with_gallium_v3d or with_gallium_vc4 or with_gallium_etnaviv or with_gallium_panfrost or with_gallium_lima or with_gallium_freedreno
 
+with_dri = false
 if with_gallium and system_has_kms_drm
   _glx = get_option('glx')
   _egl = get_option('egl')
@@ -2279,11 +2278,6 @@ endif
 if with_dri
   lines += ''
   lines += 'DRI platform:    ' + with_dri_platform
-  if dri_drivers.length() != 0 and dri_drivers != ['']
-    lines += 'DRI drivers:     ' + ' '.join(dri_drivers)
-  else
-    lines += 'DRI drivers:     no'
-  endif
   lines += 'DRI driver dir:  ' + dri_drivers_path
 endif