module.h: relocate MODULE_PARM_DESC into moduleparam.h

There are files which use module_param and MODULE_PARM_DESC
back to back.  They only include moduleparam.h which makes sense,
but the implicit presence of module.h everywhere hid the fact
that MODULE_PARM_DESC wasn't in moduleparam.h at all.  Relocate
the macro to moduleparam.h so that the moduleparam infrastructure
can be used independently of module.h

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>