RTL changes needed for iverilog v12

[M0stafaRady]

In the latest release of Iverilog, version 12.0.0, a new error has been introduced that detects mixing between old and new declaration module styles within RTL code. like the declaration here the compile resulted in the following error:

/home/rady/caravel/openframe/caravel_openframe_project//verilog/rtl/simple_spi_master.v:187: error: 'err_out' has already been declared in this scope.

Explanation of the issue is well defined in this comment by dave_59.

I will add the required RTL need.

[RTimothyEdwards]

Unnecessarily restricting syntax in cases that are perfectly unambiguous. Computer scientists should never be allowed to get near computers.