Remove unused includes in aarch64-tdep.c

Remove unused includes in aarch64-tdep.c

include-what-you-use reports:

../../../src/binutils-gdb/gdb/aarch64-tdep.c should remove these lines:
- #include "ax.h"  // lines 45-45
- #include "elf-bfd.h"  // lines 52-52
- #include "elf/aarch64.h"  // lines 53-53
- #include "infcall.h"  // lines 44-44
- #include "inferior.h"  // lines 24-24
- #include "language.h"  // lines 43-43

gdb/ChangeLog:

	* aarch64-tdep.c: Remove includes.