rust: cfi: fix `patchable-function-entry` starting version

The `-Zpatchable-function-entry` flag is available since Rust
1.81.0, not Rust 1.80.0, i.e. commit ac7595fdb1ee ("Support for -Z
patchable-function-entry") in upstream Rust.

Fixes: ca627e63 ("rust: cfi: add support for CFI_CLANG with Rust")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Fiona Behrens <me@kloenk.dev>
Link: https://lore.kernel.org/r/20240925141944.277936-1-ojeda@kernel.orgSigned-off-by: Miguel Ojeda <ojeda@kernel.org>

init/Kconfig

@@ -1948,7 +1948,7 @@ config RUST
 	depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE
 	depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers)
 	select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG
-	depends on !CALL_PADDING || RUSTC_VERSION >= 108000
+	depends on !CALL_PADDING || RUSTC_VERSION >= 108100
 	depends on !KASAN_SW_TAGS
 	help
 	  Enables Rust support in the kernel.