Update PowerPC64 symtocbase test

Using a symbol other than .TOC. with @tocbase is an extension to the
ABI.  It is never valid to use a symbol without a definition in the
binary, and symbols on these expressions cannot be overridden.  Make
this explicit by using ".hidden" in the testcase.

	* testsuite/ld-powerpc/symtocbase-1.s: Align data.  Make function
	entry symbol hidden.
	* testsuite/ld-powerpc/symtocbase-2.s: Likewise.
	* testsuite/ld-powerpc/symtocbase.d: Adjust expected output.