The use of I/O ports in the Linux driver to directly control OPL chips
is x86 specific and only really makes sense for x86-based PC's with
compatible hardware.
For some architectures (e.g. ARM), ioperm, inb and outb do exist and are
detected by the configure script (via AC_CHECK_FUNCS(ioperm)), but their
use is inappropriate in these cases and should be avoided.
In some other scenarios, like when using a GNU toolchain + uClibc for
PowerPC, the build even fails with the following error:
opl_linux.c:26:20: fatal error: sys/io.h: No such file or directory
That is so because ioperm() is exported by uClibc and gets detected by
configure, which enables the "Linux" driver via definition of
HAVE_IOPERM, but in practice 'sys/io.h' is missing for ppc (inb/outb is
not implemented, and the call to ioperm() would return EIO anyway).
So, besides testing for HAVE_IOPERM, also test if either __i386__ or
__x86_64__ are defined before enabling this OPL driver.
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