kconfig: linker: Add --no-relax build option

In some architectures the linker performs global optimization relaxing
address modes and changing intructions in the output object file. This
is a problem when userspace is enabled since it assumes that addresses
won't change after certain build stage. In no supported architectures
this option is ignored.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>