RS6000/BFD: Remove dead duplicate `config.bfd' target matchers

RS6000/BFD: Remove dead duplicate `config.bfd' target matchers

Remove duplicate `rs6000-*-aix5.[01]' and `rs6000-*-aix[5-9]*' target
configuration selectors meant to correspond to `powerpc64-*-aix5.[01]'
and `powerpc64-*-aix[5-9]*' respectively for the purpose of BFD target
vector selection in `config.bfd'.

These selectors were added with commit 9a9e2ca33263 ("rs6000 xcoff bfd
config"), <https://sourceware.org/ml/binutils/2010-12/msg00372.html>,
and have been dead right from the beginning, because they appear twice
each in the case statement, which means the earlier instance of each
takes precedence and the other one is ignored.  Here ones that alias to
`powerpc-*-aix5.[01]' and `powerpc-*-aix[5-9]*' respectively immediately
above are used instead.

	bfd/
	* config.bfd <rs6000-*-aix5.[01], rs6000-*-aix[5-9]*>: Remove
	duplicate `case' selectors.