kconfig: remove 'kvmconfig' and 'xenconfig' shorthands

stable inclusion
from stable-5.10.9
commit 17a08680ab6a6c057949cb48c352933e09ea377a
bugzilla: 47457

--------------------------------

[ Upstream commit 9bba03d4 ]

Linux 5.10 is out. Remove the 'kvmconfig' and 'xenconfig' shorthands
as previously announced.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>