Get value of gpd.tee.arith.maxBigIntSize from libutee

The property gpd.tee.arith.maxBigIntSize was implemented in TEE core by
tee_svc_sys_get_property() which was returning a constant taken from the
crypto module (LTC_MAX_BITS_PER_VARIABLE / 2).
The correct value is TEE_MAX_NUMBER_OF_SUPPORTED_BITS from libutee.
This commit makes libutee return the appropriate value directly (without
calling the TEE core) and deletes the property from the syscall.
Additionally, this removes the unjustified dependency of tee_svc.c on
<tee_ltc_wrapper.h>.