drivers: ethernet: nxp_enet: Fused MAC address fixes

Add required initialisation of OCOTP. The IMXRT10XX
variants don't support fuseWords to be greater than 1.
MAC0 fuse map address is 0x22 instead of 0x620.
Fill in mac_addr buffer correctly.

Signed-off-by: Matthias Alleman <matthias.alleman@basalte.be>
(cherry picked from commit 931628a7)