Kernel 4.19.47 added a new kernel config symbol ARM64_ERRATUM_1463225.
This causes a build failure for sunxi/cortexa53. Add the symbol to the
generic config to fix this, and avoid future build failures on other
arm64 targets that expose this symbol. As the erratum only affects
Cortex-A76 cores, we can safely disable it.
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>