wwan: iosm: use a flexible array rather than allocate short objects

wwan: iosm: use a flexible array rather than allocate short objects

GCC array-bounds warns that ipc_coredump_get_list() under-allocates
the size of struct iosm_cd_table *cd_table.

This is avoidable - we just need a flexible array. Nothing calls
sizeof() on struct iosm_cd_list or anything that contains it.

Reviewed-by: M Chetan Kumar <m.chetan.kumar@intel.com>
Link: https://lore.kernel.org/r/20220520060013.2309497-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>