custombootimg.mk: Fix board name and force v2

As shown in https://github.com/AdFad666/cauliflower-meringue/commit/2e15dcb93e90db24e7214828b7a4be161249e88b

Change-Id: I8d0cd4268d85d87ef45b79dc09a5236a8a2fa5c1
Move to userdebug

eng is useless

Change-Id: I89f7872ced85acadb3f26708063a5fb569493a0b
Fix product name

D got lost somewhere?

Change-Id: I0df4bb0f075af772fc566d9e91909a28b6138482