stm32mp: stm32prog: Add CONFIG_CMD_STM32PROG_SERIAL and _USB

Add CONFIG_CMD_STM32PROG_SERIAL and CONFIG_CMD_STM32PROG_USB to
independently select the support of UART or USB communication for
STM32CubeProgrammer.

For serial boot over UART, user can deactivate CONFIG_CMD_STM32PROG_SERIAL
to use U-Boot console of binary loaded by UART (for board bring-up for
example).

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>