msm: mdss: refactor register space io remap to use common utility

Refactor MDSS and VBIF registers ioremap to go through common utility
functions and add API to allow adding any register base which uses
utility structure. Expose VBIF register base through this utility.

Change-Id: I97ca2db07e40b261abf1a46b427a373295886cb2
Signed-off-by: Adrian Salido-Moreno <adrianm@codeaurora.org>