UBSan: Define FST LLT macros without integer overflow

UBSan: Define FST LLT macros without integer overflow

FST_MAX_LLT_MS definition depended on undefined behavior with unsigned
integer overflow. Avoid that and also optimize the
FST_LLT_{MS_TO_VAL,VAL_TO_MS} macros to handle larger values without
overflowing 32-bit unsigned integers.

fst_session.c:1274:52: runtime error: unsigned integer overflow: 4294967295 * 32 cannot be represented in type 'unsigned int'

Signed-off-by: Jouni Malinen <j@w1.fi>