or1k/libgcc: make internal calls to __udivsi3 hidden

This way, the relocations can be resolved at link time and
there will be no R_OR1K_INSN_REL_26 relocs in libgcc_s.so.
or1k: define ASM_PREFERRED_EH_DATA_FORMAT

By defining ASM_PREFERRED_EH_DATA to DW_EH_PE_pcrel when
compiling with -fPIC, unaligned R_OR1K_32 relocs in .eh_frame
are avoided.