2711: HDMI: EXPERIMENTAL - Dual HDMI support

NOTE: Dual HDMI mode is only enabled if hdmi_test | 0x2 != 0

The reason for conditionally enabling dual HDMI mode because this might
cause problems if force_hotplug is enabled. Instead of enabling one
display this would enable two displays. A proper configuration for
dual HDMI has yet to be designed.

Change the static state to arrays of state structures indexed by HDMI
core.

It compiles and both HDMI cores seem to work individually.

Concurrent display usage works with one display just displaying the HVS
background colour.

HDCP functions have NOT been updated. The code won't compile if
WANT_HDCP is enabled. HDCP isn't supported on Raspberry Pi and the 2711
HDCP functionality has changed so this would need re-writing anyway.

TODO:
* Create hdmi_primary instead of using C(hdmi_core) everywhere
* Fix issue where hotplug of HDMI0 causes missaligned exception in EOF
  frame handler for core 0 - seems to only happen with logging enabled
  and might be a long standing issue.

interface/vmcs_host/vc_dispmanx_types.h

@@ -62,6 +62,8 @@ typedef uint32_t DISPMANX_PROTECTION_T;
 #define DISPMANX_ID_FORCE_LCD 4
 #define DISPMANX_ID_FORCE_TV  5
 #define DISPMANX_ID_FORCE_OTHER 6 /* non-default display */
+#define DISPMANX_ID_HDMI2     7
+#define DISPMANX_ID_FORCE_TV2 8
 
 /* Return codes. Nonzero ones indicate failure. */
 typedef enum {