PIPE_MBUS_DBOX_CTL was only being programmed when a pipe is being
enabled but that could potentially cause issues as it could have
mismatching values while pipes are being enabled.

So here moving the PIPE_MBUS_DBOX_CTL programming of all pipes to be
executed before the function that enables all pipes, leaving all pipes
with a matching A_CREDIT value.

While at it, also moving it to intel_pm.c as we are trying to reduce
the gigantic size of intel_display.c and intel_pm.c have other MBUS
programing sequences.

v2:
- do not program PIPE_MBUS_DBOX_CTL if pipe will not be active or
when it do not needs modeset
- remove the checks to wait a vblank

v3:
- checking if dbuf state is present in state before using it

v4:
- removing redundant checks
- calling intel_atomic_get_new_dbuf_state instead of
intel_atomic_get_dbuf_state

BSpec: 49213
BSpec: 50343
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220330155724.255226-3-jose.souza@intel.com