intel: Remove GFXUMA and related global variables

Remove use of global variables uma_memory_base and uma_memory_size
from builds with Intel northbridges, as these variables can be kept
within the chipset or even as stack locals.

Intel platforms have no functional implemenation for option GFXUMA.
If we did implement some choice between external and integrated graphics,
it needs to be named in less obscure fashion.

Change-Id: I12f18c4ee6bc89e65a561db6c2b514956f3e2d03
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/5720
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>

src/northbridge/intel/i945/northbridge.c

@@ -87,6 +87,7 @@ static void pci_domain_set_resources(device_t dev)
 	uint8_t tolud, reg8;
 	uint16_t reg16;
 	unsigned long long tomk, tomk_stolen;
+	uint64_t uma_memory_base = 0, uma_memory_size = 0;
 	uint64_t tseg_memory_base = 0, tseg_memory_size = 0;
 
 	/* Can we find out how much memory we can use at most