soc: andestech: linker.ld: Handle symtab/strtab/shstrtab to fix warnings

lld will produce warnings for the symtab, strtab, and shstrtab sections
if --orphan-handling=warn is specified and there are no matching rules
in the linker script for these sections. Handle these sections when
building with lld to prevent the warnings.

This is exactly the same as commit
c420733c, but for the AE350 linker
script.

Signed-off-by: Tom Hughes <tomhughes@chromium.org>