Fix missing mapping for display_transform

Fix missing mapping for display_transform

Currently the display transform set in the hwc_display.ini file
is according to the HWCRotation enums but the values expected in
Validate transfrom are 0,4,8,16. Instead of directly mapping 0..3
to 0,4,8,16, accept 0..3 as inputs as it simplifies the calculation
of the final plane rotation because 0..3 forms a circulant matrix
over modulo 4 arithmetic.

Jira: None
Tests: If the requested layer rotation if 0 degree and the display
       rotation set in ini file is 90 then the final rotation should
       be 90 degrees.

Signed-off-by: Harish Krupo <harish.krupo.kps@intel.com>