[otbn] Fix timing of base RF writes for BN.LID
[otbn] Fix timing of base RF writes for BN.LID

When using an increment along with the call stack (x1) reads and writes
need to to occur at the appropriate point so the call stack push and pop
occur together.

Fixes #7579

Signed-off-by: Greg Chadwick <3e4c3d6d87c017d1a2fa161477653b4039c6b2fb@lowrisc.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan