boot/uboot.mk: new zynqmp pmufw prebuilt option

The new BR2_TARGET_UBOOT_ZYNQMP_PMUFW_PREBUILT option will enable u-boot to
use the xilinx-prebuilt package for downloading a pmufw.elf that gets included
in the generated boot.bin.

If the BR2_TARGET_UBOOT_ZYNQMP_PMUFW_PREBUILT option is enabled, then the
BR2_TARGET_UBOOT_ZYNQMP_PMUFW config for downloading a prebuilt pmufw will
be ignored.

Signed-off-by: Neal Frager <neal.frager@amd.com>
Reviewed-by: Brandon Maier <brandon.maier@collins.com>
[yann.morin.1998@free.fr:
  - add 'custom' to prompt for BR2_TARGET_UBOOT_ZYNQMP_PMUFW
  - fix checkpackage
]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
2 files changed