static_call_inline: Provide trampoline address when updating sites

In preparation of support of inline static calls on powerpc, provide
trampoline address when updating sites, so that when the destination
function is too far for a direct function call, the call site is
patched with a call to the trampoline.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/5efe0cffc38d6f69b1ec13988a99f1acff551abf.1733245362.git.christophe.leroy@csgroup.eu

arch/x86/kernel/static_call.c

@@ -158,7 +158,7 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
 {
 	mutex_lock(&text_mutex);
 
-	if (tramp) {
+	if (tramp && !site) {
 		__static_call_validate(tramp, true, true);
 		__static_call_transform(tramp, __sc_insn(!func, true), func, false);
 	}

kernel/static_call_inline.c

@@ -206,7 +206,7 @@ void __static_call_update(struct static_call_key *key, void *tramp, void *func)
 				continue;
 			}
 
-			arch_static_call_transform(site_addr, NULL, func,
+			arch_static_call_transform(site_addr, tramp, func,
 						   static_call_is_tail(site));
 		}
 	}