s390x sframe regressions

Commit 6ab3f09a682a resulted in regressions.
s390x-linux-gnu  FAIL: SFrame simple link
s390x-linux-gnu  FAIL: SFrame for plt0 and pltN

Commit 939eb467b21d exposed the problem further.
s390x-linux-gnu  FAIL: LTO 4a
s390x-linux-gnu  FAIL: LTO 4c
s390x-linux-gnu  FAIL: LTO 4d

	* elf64-s390.c (elf_s390_create_dynamic_sections): Set plt_sframe
	ELF section type.

Reviewed-by: Jens Remus <jremus@linux.ibm.com>