zms: optimize cache for settings subsystem

Settings subsystem is storing the name ID and the linked list node ID
with only one bit difference at BIT(0).
Settings subsystem is also storing the name ID and the data ID in two
different ZMS entries at an exact offset of ZMS_DATA_ID_OFFSET.
Using the regular lookup function could result in many cache misses.

Therefore, to assure the least number of collisions in the lookup cache,
the BIT(0) of the hash indicates whether the given ZMS ID represents a
linked list entry or not, the BIT(1) indicates whether the ZMS ID is a
name or data and the remaining bits of the hash are set to a truncated
part of the original hash generated by Settings.

Signed-off-by: Riadh Ghaddab <rghaddab@baylibre.com>