board: stm32mp1: set environment variable fdtfile

For booting Linux in the generic distro mechanism and support of
FDTDIR in extlinux.conf , cmd/pxe.c retrieves the FDT file name
from "fdtfile" environment variable.

Dynamically build this variable with compatible of STMicroelectronics
boards.

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