We are about to add more complexity to vblank length check. It makes sense
to move it to separate function for sake of clarity.

v2: change name to wake_lines_fit_into_vblank
Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240607134917.1327574-11-jouni.hogander@intel.com