[ARC] don't force _init/_fini as DT_INIT/DT_FINI.

[ARC] don't force _init/_fini as DT_INIT/DT_FINI.

Recent gcc commit b4371b277f1e ("[ARC] Enable init_array support")
inhibits DT_"INIT,FINI} in favor of DT_{INIT,FINI}ARRAY.

Even prior to that, it seems ARC port is the only one with this
special DT_INIT/FINI handling in linker emulation. Removing it
doesn't seem to change any uClibc/glibc testsuite results,
so this can RIP anyways.

bfd/
    2019-02-01  Vineet Gupta <vgupta@synopsys.com>

           * elf32-arc.c: Delete init_str, fini_str

ld/
    2019-02-01  Vineet Gupta <vgupta@synopsys.com>

           * emultempl/arclinux.em : Delete special INIT/FINI handling.