sunxi: Fix CONFIG_SUNXI_GMAC references

sunxi: Fix CONFIG_SUNXI_GMAC references

SUNXI_GMAC was still used to configure the code where as the
same has been renamed and moved to Kconfig in below commit
"sunxi: Move SUNXI_GMAC to Kconfig"
(sha1: 4d43d065db3262f9a9918ba72457bf36dfb8e0bb)

Signed-off-by: Dave Prue <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Reviewed-by: Jagan Teki <[email protected]>
Reviewed-by: Mark Kettenis <[email protected]>
Tested-by: Mark Kettenis <[email protected]>
[Tweek commit message, config_whitelist.txt, build-whitelist.sh]
Signed-off-by: Jagan Teki <[email protected]>