openpiton: riscv64: Drop unnecessary 'imply SPL_RISCV_MMODE'

As the code is today, we get a warning about "select" statements on
"choice" options not doing anything. In this case, the option
SPL_RISCV_MMODE is the default.

Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Tianrui Wei <tianrui-wei@outlook.com>
1 file changed