[dv/dv_base_reg] change from uvm_low to uvm_high
[dv/dv_base_reg] change from uvm_low to uvm_high

Change the verbosity of a uvm_info to avoid massive print in the nightly
regression.

Signed-off-by: Cindy Chen <399ad771a111eac8923348b1e2af093034e5d4f1@opentitan.org>

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