Bluetooth: host: Fix array overrun of client features bitset

Fix array overrun of client features bitset, where CF_BYTE_LAST was
incorrectly defined as 2 using module instead of divide.
Also fix additional bit-logic when number of bits would exceed a byte:
 - Inner for loop iterates from 0 to number of bits on a single byte.
 - Same bitmask used for all bytes.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>