drm/i915: Add parsing support for new MIPI blocks in VBT

The parser extracts the config block(#52) and sequence(#53) data
and store in private data structures.

v2: Address review comments by Jani
    - adjust code for the structure changes for bdb_mipi_config
    - add boundry and buffer overflow checks as suggested
    - use kmemdup instead of kmalloc and memcpy

v3: More strict check while parsing VBT
    - Ensure that at anytime we do not go beyond sequence block
      while parsing
    - On unknown element fail the whole parsing

v4: Style changes and spell check mostly as suggested by Jani

Signed-off-by: Shobhit Kumar <shobhit.kumar@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>