So far models of the Dell Venue 8 Pro, with a panel with MIPI panel
index = 3, one of which has been kindly provided to me by Jan Brummer,
where not working with the i915 driver, giving a black screen on the
first modeset.

The problem with at least these Dells is that their VBT defines a MIPI
ASSERT sequence, but not a DEASSERT sequence. Instead they DEASSERT the
reset in their INIT_OTP sequence, but the deassert must be done before
calling intel_dsi_device_ready(), so that is too late.

Simply doing the INIT_OTP sequence earlier is not enough to fix this,
because the INIT_OTP sequence also sends various MIPI packets to the
panel, which can only happen after calling intel_dsi_device_ready().

This commit fixes this by splitting the INIT_OTP sequence into everything
before the first DSI packet and everything else, including the first DSI
packet. The first part (everything before the first DSI packet) is then
used as deassert sequence.

Changed in v2:
-Split the init OTP sequence into a deassert reset and the actual init
 OTP sequence, instead of calling it earlier and then having the first
 mipi_exec_send_packet() call call intel_dsi_device_ready().

Changes in v3:
-Move the whole shebang to intel_bios.c

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=82880
References: https://bugs.freedesktop.org/show_bug.cgi?id=101205
Cc: Jan-Michael Brummer <jan.brummer@tabos.org>
Reported-by: Jan-Michael Brummer <jan.brummer@tabos.org>
Tested-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214082151.25015-3-hdegoede@redhat.com