libhardware: Add new display types.

- Extend display types enums to support multiple displays.
- Reserve display types 2 to 4 for additional external displays.
- Reserve display types 5 to 7 for additional builtin displays.
- Move virtual display type to 8.

CRs-Fixed: 2274419
Change-Id: I9a0f5167a777a1d903eb98c5aa7ee0b229d08640
1 file changed