dt-bindings: Add support for GDSC flag to map single GDSCR

Add new gdsc flag "qcom,no-config-gdscr" to map a single
register for GDSC, as few legacy HW have support only
for single GDSCR and don't contain config GDSCR's.

Change-Id: I89996d05e6ee0fd321c63f0c91af6b5b3c313b0d