The following patch fixed the assembly / disassembly of the rfebb instruction:
https://sourceware.org/ml/binutils/2015-06/msg00190.html
This patch updates the gdb testsuite to match the new disassembly behavior.
gdb/testsuite/
* gdb.arch/powerpc-power.exp <rfebb>: Fixup test results.
* gdb.arch/powerpc-power.s <rfebb>: Likewise.