[ot] scripts/opentitan: cfggen.py: Update OTP constant SV file location

After changes in OpenTitan to move otp_ctrl to ipgen, to keep QEMU
working with `master` we need to source the OTP constant SV file from
the correct location. This default location is top-specific.

Signed-off-by: Alex Jones <alex.jones@lowrisc.org>

Author: AlexJones0

scripts/opentitan/cfggen.py

@@ -285,7 +285,9 @@ def main():
             argparser.error(f"No such file '{lcpath}'")
 
         if not args.otpconst:
-            ocpath = joinpath(ot_dir, 'hw/ip/otp_ctrl/rtl/otp_ctrl_part_pkg.sv')
+            otp_ctrl = f'hw/{top}/ip_autogen/otp_ctrl/'
+            otp_constant_file = 'rtl/otp_ctrl_part_pkg.sv'
+            ocpath = joinpath(ot_dir, otp_ctrl, otp_constant_file)
         else:
             ocpath = args.otpconst
         if not isfile(lcpath):