kconfig: remove 'kvmconfig' and 'xenconfig' shorthands

Linux 5.10 is out. Remove the 'kvmconfig' and 'xenconfig' shorthands
as previously announced.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/kconfig/Makefile

@@ -94,16 +94,6 @@ configfiles=$(wildcard $(srctree)/kernel/configs/$@ $(srctree)/arch/$(SRCARCH)/c
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/kconfig/merge_config.sh -m .config $(configfiles)
 	$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
 
-PHONY += kvmconfig
-kvmconfig: kvm_guest.config
-	@echo >&2 "WARNING: 'make $@' will be removed after Linux 5.10"
-	@echo >&2 "         Please use 'make $<' instead."
-
-PHONY += xenconfig
-xenconfig: xen.config
-	@echo >&2 "WARNING: 'make $@' will be removed after Linux 5.10"
-	@echo >&2 "         Please use 'make $<' instead."
-
 PHONY += tinyconfig
 tinyconfig:
 	$(Q)$(MAKE) -f $(srctree)/Makefile allnoconfig tiny.config