Declutter find_compression_limit() a bit by extracting
intel_fbc_stolen_end().
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210610183237.3920-8-ville.syrjala@linux.intel.comReviewed-by: NJosé Roberto de Souza <jose.souza@intel.com>