gdb: fix aarch64 remote debugging gdb/28355

The raspberry3-64 machine from meta-raspberrypi is affected by this bug.

https://sourceware.org/bugzilla/show_bug.cgi?id=28355
https://sourceware.org/git/?p=binutils-gdb.git;a=patch;h=eb79b2318066cafb75ffdce310e3bbd44f7c79e3
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=7fd8546853e3f0333ba8d8238413aba7eb45c69f



Signed-off-by: Matthias Klein <matthias@extraklein.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>