build: Drop CONFIG_$ARCH_$(XEN_OS) definitions

These aren't used, and are not obvious useful either.

tools/ does have some logic which works on $(XEN_OS) directly, and some on
CONFIG_$(XEN_OS) too, but this isn't how we typically refer to things.

The only user ever of this scheme (AFAICT) was introduced in
c0fd920e98 (2006) and deleted in fa2244104b (2010).

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Jiamei Xie <jiamei.xie@arm.com>

config/arm32.mk

@@ -1,6 +1,5 @@
 CONFIG_ARM := y
 CONFIG_ARM_32 := y
-CONFIG_ARM_$(XEN_OS) := y
 
 CONFIG_XEN_INSTALL_SUFFIX :=
 

config/arm64.mk

@@ -1,6 +1,5 @@
 CONFIG_ARM := y
 CONFIG_ARM_64 := y
-CONFIG_ARM_$(XEN_OS) := y
 
 CONFIG_XEN_INSTALL_SUFFIX :=
 

config/riscv64.mk

@@ -1,5 +1,4 @@
 CONFIG_RISCV := y
 CONFIG_RISCV_64 := y
-CONFIG_RISCV_$(XEN_OS) := y
 
 CONFIG_XEN_INSTALL_SUFFIX :=

config/x86_32.mk

@@ -1,6 +1,5 @@
 CONFIG_X86 := y
 CONFIG_X86_32 := y
-CONFIG_X86_$(XEN_OS) := y
 
 CONFIG_MIGRATE := y
 CONFIG_XCUTILS := y

config/x86_64.mk

@@ -1,6 +1,5 @@
 CONFIG_X86 := y
 CONFIG_X86_64 := y
-CONFIG_X86_$(XEN_OS) := y
 
 CONFIG_MIGRATE := y
 CONFIG_XCUTILS := y