net: apple: Fix manufacturer name in Kconfig help text

The help text refers to IBM instead of Apple, presumably because it was
copied from the former.

Fixes: 8fb6b090

 ("bmac/mace/macmace/mac89x0/cs89x0: Move the Macintosh (Apple) drivers")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: David S. Miller <davem@davemloft.net>