[ spi_host ] Remove cmd_len_q register to clean up DC logs
[ spi_host ] Remove cmd_len_q register to clean up DC logs

The register cmd_len_q is never used and gets optimized away at synthesis. This commit explicitly
removes that register (and comments the code as such) to clean up the logs.

Signed-off-by: Martin Lueker-Boden <7e82c17fafb3b7b91b3c3396a2f21a060e5a6c3d@wdc.com>

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