parisc: Enable CONFIG_MLONGCALLS by default

Enable the -mlong-calls compiler option by default, because otherwise in most
cases linking the vmlinux binary fails due to truncations of R_PARISC_PCREL22F
relocations. This fixes building the 64-bit defconfig.

Cc: stable@vger.kernel.org # 4.0+
Signed-off-by: Helge Deller <deller@gmx.de>