package/gdb: Enable OpenRISC GDB support

The OpenRiSC gdb port has supported native debugging since version 8.3
and remote debugging since before that.  So it is now safe to enabled
this.

This patch removes the conditions blocking gdb from being built on or1k
architecture builds.

Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>