libckteec: Add helper to convert TA's CK_ULONG to REE's CK_ULONG

On 64 bit systems uint32_t cannot handle CK_ULONG defined
CK_UNAVAILABLE_INFORMATION.

This adds helper maybe_unavail() to assist in conversion.

Signed-off-by: Vesa Jääskeläinen <vesa.jaaskelainen@vaisala.com>
Reviewed-by: Etienne Carriere <etienne.carriere@foss.st.com>