ARM: vexpress: Start using new Versatile Express infrastructure

This patch starts using all the configuration infrastructure.

- generic GPIO library is forced now

- sysreg GPIOs are used as MMC CD and WP information sources;
  thanks to this MMCI auxiliary data is not longer necessary

- DVI muxer and mode control is removed from non-DT V2P-CA9 code
  as this is now handled by the vexpress-dvi driver

- clock generators control is removed as is being handled by the
  common clock driver now

- the sysreg and sysctl control is now delegated to the
  appropriate drivers and all related code was removed

- NOR Flash set_vpp function has been removed as the control
  bit used does _not_ control its VPP line, but the #WP signal
  instead (which is de facto unusable in case of Linux MTD
  drivers); this also allowed the remove its DT auxiliary
  data

The non-DT code defines only minimal required number of
the config devices. Device Trees are updated to make use
of all new features.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>