rtc: bq4802: add sparc dependency

The added HAS_IOPORT dependency might not actually be necessary as Geert
points out, but the driver is also only used on one architecture. Sparc
is also a special case here since it converts port numbers into virtual
addresses rather than having them mapped into a particular part of the
__iomem address space, so the difference is actually not important here.

Add a dependency on sparc, but allow compile-testing otherwise, to
make this clearer without anyone having to spend much time modernizing
the driver beyond that.

Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: David S. Miller <davem@davemloft.net>
Link: https://lore.kernel.org/all/CAMuHMdWEx0F=fNei4Bz_JPkuvoaN-+zk08h0i8KnSi_VjO615g@mail.gmail.com/


Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20230719192835.1025406-1-arnd@kernel.org


Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>