[gdb/testsuite] Fix gdb.tui/resize-3.exp on ppc64-linux

On ppc64-linux, with test-case gdb.tui/resize-3.exp I run into:
...
FAIL: gdb.tui/resize-3.exp: after resize: Assembler for foo is shown
...
because the disassembly window shows:
...
    0 +----------------------------------------------------------------------+
    1 |   0x10000093c <.foo>                      std     r31,-8(r1)         |
    2 |   0x100000940 <.foo+4>                    stdu    r1,-64(r1)         |
    3 |   0x100000944 <.foo+8>                    mr      r31,r1             |
    4 |B+>0x100000948 <.foo+12>                   li      r9,0               |
...
and we grep for "<foo".

Fix this by updating the regexp.

Tested on ppc64-linux and x86_64-linux.
1 file changed