Adjust some strip testcases to silence h8300 warnings
* testsuite/binutils-all/strip-13mips64.s: Add section flags
for reloc section.
* testsuite/binutils-all/strip-13rel.s: Likewise.
* testsuite/binutils-all/strip-13rela.s: Likewise.
* testsuite/binutils-all/strip-14mips64.s: Likewise.
* testsuite/binutils-all/strip-14rel.s: Likewise.
* testsuite/binutils-all/strip-14rela.s: Likewise.
* testsuite/binutils-all/strip-15mips64.s: Likewise.
* testsuite/binutils-all/strip-15rel.s: Likewise.
* testsuite/binutils-all/strip-15rela.s: Likewise.