input: Controller unique mapping (preliminary)

Add ini option `unique_mapping` which makes controller mappings unique to the physical port the controller is connected to.
Calculates a uint32_t unique_hash for each device during enumeration.

Co-authored-by: Martin Donlon <github-martin@donlons.com>

cfg.cpp

@@ -119,6 +119,7 @@ static const ini_var_t ini_vars[] =
 	{ "HDR_AVG_NITS", (void*)(&(cfg.hdr_avg_nits)), UINT16, 100, 10000},
 	{ "VGA_MODE", (void*)(&(cfg.vga_mode)), STRING, 0, sizeof(cfg.vga_mode) - 1 },
 	{ "NTSC_MODE", (void *)(&(cfg.ntsc_mode)), UINT8, 0, 2},
+	{ "UNIQUE_MAPPING", (void *)(&(cfg.unique_mapping)), UINT8, 0, 1},
 };
 
 static const int nvars = (int)(sizeof(ini_vars) / sizeof(ini_var_t));