alternatives only work correctly on non-xip-kernels and while the
selected alternative-symbol has the correct dependency the symbol
selecting it also needs that dependency.

So add the missing dependency to the T-Head errata Kconfig symbol.
Reported-by: Nkernel test robot <yujie.liu@intel.com>
Reviewed-by: NGuo Ren <guoren@kernel.org>
Signed-off-by: NHeiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220526205646.258337-5-heiko@sntech.de
Fixes: a35707c3 ("riscv: add memory-type errata for T-Head")
Signed-off-by: NPalmer Dabbelt <palmer@rivosinc.com>