[POWERPC] 8xx: Remove unused m8xx_cpm_hostalloc/free/dump()

m8xx_cpm_hostalloc is still defined in commproc.c, but no users are left
in the kernel tree. m8xx_cpm_hostfree and m8xx_cpm_hostdump are only
defined in the headers. Remove this dead code.

Signed-off-by: Jochen Friedrich <jochen@scram.de>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>