[binutils-gdb] Update GDB test case for new lnia extended mnemonic.

[sergiodj+buildbot@sergiodj.net]

*** TEST RESULTS FOR COMMIT 66953522c9061874047d2e9832c206af783c971c ***

Author: Peter Bergner <bergner@vnet.ibm.com>
Branch: master
Commit: 66953522c9061874047d2e9832c206af783c971c

Update GDB test case for new lnia extended mnemonic.

When I added the new lnia extended mnemonic for addpcis, I updated the
assembler/disassembler test cases, but overlooked the GDB test cases.
This patch fixes that oversight and associated test case failure.

	* gdb.arch/powerpc-power9.exp: Update test case for new lnia
	extended mnemonic.
	* gdb.arch/powerpc-power9.s: Likewise.