device/device.c: Rename .disable to .vga_disable

This makes it clear what this function pointer is used for.

Change-Id: I2090e164edee513e05a9409d6c7d18c2cdeb8662
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51009
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/northbridge/intel/sandybridge/gma.c

@@ -646,7 +646,7 @@ static struct device_operations gma_func0_ops = {
 	.enable_resources       = pci_dev_enable_resources,
 	.acpi_fill_ssdt		= gma_generate_ssdt,
 	.init                   = gma_func0_init,
-	.disable                = gma_func0_disable,
+	.vga_disable                = gma_func0_disable,
 	.ops_pci                = &pci_dev_ops_pci,
 	.acpi_name              = gma_acpi_name,
 };