[fpv] fix random seed syntax error
[fpv] fix random seed syntax error

FPV does not support rand dist and FPV_INIT with a non-constant.
So this PR fixes the syntax error by using the default LFSR seed.

Signed-off-by: Cindy <399ad771a111eac8923348b1e2af093034e5d4f1@google.com>

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