makefiles: Build lm32 firmware as part of generate step.
makefiles: Build lm32 firmware as part of generate step.

cr1901/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,cr1901/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware,mithro/HDMI2USB-litex-firmware