drm/i915/psr: Check that vblank is long enough for psr2

Ensure vblank >= psr2 vblank
where
Psr2 vblank = PSR2_CTL Block Count Number maximum line count.

Bspec: 71580, 49274

v2: Use calculated block count number maximum line count

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230329150703.432072-6-jouni.hogander@intel.com