[otp rtl] Fix warning
[otp rtl] Fix warning

This change fixes the following warning:
```
Warning-[DTIE] Different enum types in equality
../src/lowrisc_ip_otp_ctrl_0.1/rtl/otp_ctrl_scrmbl.sv, 156
otp_ctrl_scrmbl, "(data_state_sel == SelDigestConst)"
  Enum values 'data_state_sel' and 'SelDigestConst' of different enum types
  are used together with equality operator '=='.
  LHS type: enum 'data_state_sel_e' defined in scope 'otp_ctrl_scrmbl_0000' at
  "../src/lowrisc_ip_otp_ctrl_0.1/rtl/otp_ctrl_scrmbl.sv", 128
  RHS type: enum 'key_state_sel_e' defined in scope 'otp_ctrl_scrmbl_0000' at
  "../src/lowrisc_ip_otp_ctrl_0.1/rtl/otp_ctrl_scrmbl.sv", 136
```

The change fixes the offending assertion.

Signed-off-by: Srikrishna Iyer <2803d640feace36379942447842f26c7747b4dc3@google.com>

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