loongarch: Don't check ABI flags if no code section

loongarch: Don't check ABI flags if no code section

Various packages (glib and gtk4 for example) produces data-only objects
using `ld -r -b binary` or `objcopy`, with no elf header flags set.  But
these files also have no code sections, so they should be compatible
with all ABIs.

bfd/
	* elfnn-loongarch.c (elfNN_loongarch_merge_private_bfd_data):
	Skip ABI checks if the input has no code sections.

Reported-by: Wu Xiaotian <yetist@gmail.com>
Suggested-by: Wang Xuerui <i@xen0n.name>
Signed-off-by: Xi Ruoyao <xry111@mengyan1223.wang>