Ignore issue-122805.rs on big endian

Due to the use of to_be(), this codegen test is only applicable to
little-endian. The test tries to handle this via
`#[cfg(target_endian = "little")]`, which means that the function
will be omitted entirely and the CHECK lines will not match.
Instead, skip the test on big endian entirely.

Author: nikic

tests/codegen/issues/issue-122805.rs

@@ -7,6 +7,7 @@
 //@ [OPT3LINX64] only-x86_64
 //@ [OPT3WINX64] only-x86_64
 //@ min-llvm-version: 18.1.3
+//@ ignore-endian-big
 
 #![crate_type = "lib"]
 #![no_std]
@@ -39,7 +40,6 @@
 // OPT3WINX64-NEXT: store <8 x i16>
 // CHECK-NEXT: ret void
 #[no_mangle]
-#[cfg(target_endian = "little")]
 pub fn convert(value: [u16; 8]) -> [u8; 16] {
     let addr16 = [
         value[0].to_be(),