[PATCH] broken dependency for I2C_MPC

All boards dealt with by I2C_MPC are 32bit.  Moreover, driver simply
won't build on ppc64 - it uses ppc32-only types all over the place. 
Dependency fixed - it's PPC32, not PPC. 

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>