moduleparam: fix alpha, ia64 and ppc64 compile failures

On alpha, ia64 and ppc64 only relocations to local data can go into
read-only sections. The vast majority of module parameters use the global
generic param_set_*/param_get_* functions, so the 'const' attribute for
struct kernel_param is not only useless, but it also causes compile
failures due to 'section type conflict' in those rare cases where
param_set/get are local functions.

This fixes http://bugzilla.kernel.org/show_bug.cgi?id=8964



Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Adrian Bunk <bunk@kernel.org>