x86/sev: Carve out the SVSM code into a separate compilation unit

Move the SVSM-related machinery into a separate compilation unit in
order to keep sev/core.c slim and "on-topic".

No functional changes.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20251204124809.31783-4-bp@kernel.org

Author: bp3tk0v

arch/x86/coco/sev/Makefile

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-y += core.o noinstr.o vc-handle.o
+obj-y += core.o noinstr.o vc-handle.o svsm.o
 
 # Clang 14 and older may fail to respect __no_sanitize_undefined when inlining
 UBSAN_SANITIZE_noinstr.o	:= n