staging: gasket: apex: remove unused array cm_mappable_regions

Array cm_mappable_regions is defined but is never used hence it is
redundant and can be removed.

Cleans up clang warning:
warning: 'cm_mappable_regions' defined but not used [-Wunused-const-variable=]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>