The EFI loader has some code to check the size (rows and columns) of an
attached terminal. Move this over to the serial uclass so that it can be
used elsewhere.
Create a new CONFIG_SERIAL_TERM_PRESENT to control whether it should be
used. Enable that for the EFI loader to preserve existing behaviour.
Adjust the implementation so that it returns a useful error code on
failure. Put the ESC and cESC values in the serial.h header.
Signed-off-by: Simon Glass <sjg@chromium.org>
aa1cd00676