powerpc/xics: Include missing header

Include of_adresses.h to get of_iomap() prototype.

Fixes: 86c38fec ("powerpc: Remove asm/prom.h from all files that don't need it")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f20a14be1a29fa0a9ebcfc5ebf05eb69c5120d10.1653370502.git.christophe.leroy@csgroup.eu