mhi: core: remove firmware info from devicetree

It's not recommended to put firmware information inside
devicetree, get firmware information from mhi control
driver instead of devicetree.

CRs-Fixed: 2258358
Change-Id: Icdb32d674ce5a962733398149e420d5ffed1607c
Signed-off-by: Sujeev Dias <sdias@codeaurora.org>