[otbn] Fix bad_insn_addr ERR_BITS description
[otbn] Fix bad_insn_addr ERR_BITS description

Write to IMEM cannot occur from OTBN, so bad_insn_addr will only be
signalled on IMEM reads from OTBN.

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

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