drm/panic: Do not select DRM_KMS_HELPER

drm/panic: Do not select DRM_KMS_HELPER

DRM core code cannot call into DRM helper code, as this would lead to
circular references in the modular case.  Hence drop the selection of
DRM_KMS_HELPER.  It was unused anyway, as v10 switched from using
the DRM format helpers to its own color format conversion, cfr. commit
9544309775c3 ("drm/panic: Add support for color format conversion").

Remove the unneeded include of <drm/drm_format_helper.h>.

Fixes: bf9fb17c6672 ("drm/panic: Add a drm panic handler")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/60155f8c939ed286e324a7c12a1daa69fe49fcf6.1719391132.git.geert+renesas@glider.be