i2c: icy: Fix build with CONFIG_AMIGA_PCMCIA=n

i2c: icy: Fix build with CONFIG_AMIGA_PCMCIA=n

This has been found by the Kernel Test Robot:
http://lkml.iu.edu/hypermail/linux/kernel/2006.0/06862.html

With CONFIG_AMIGA_PCMCIA=n, io_mm.h does not pull in amigahw.h and
ZTWO_VADDR is undefined. Add forgotten include to i2c-icy.c

Fixes: b5bfdd14dc15 ("i2c: Add i2c-icy for I2C on m68k/Amiga")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Max Staudt <max@enpas.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>