[entropy_src/rtl] fix for halt/start sequence
[entropy_src/rtl] fix for halt/start sequence

Timing of setting register bits needed to be coordinated.

Signed-off-by: Mark Branstad <d7ca710cc6ec5dc810c866dae5369b19445fbeef@wdc.com>

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