LoongArch: Avoid orphan input sections

Ensure that all input sections are listed explicitly in the linker
script, and issue a warning otherwise. This ensures that the binary
image matches the PE/COFF and other image metadata exactly, which is
important for things like code signing.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>