configs: nitrogen*: bump kernel and u-boot revision

configs: nitrogen*: bump kernel and u-boot revision

Here are the main U-Boot modifications:
- Add Spansion flash support
- Add secure boot (HAB) support

Here are the main Linux modifications:
- Add HDMI2CSI 75Hz support
- Add KD024FM display support
- Fix PCIe reset gpios in device tree
- Backport xhci fixes from mainline
- Fix SOM PHY address bug
- Enable IPU Prefetch engine for 6QP
- Fix ft5x06 touch bug

Signed-off-by: Gary Bisson <gary.bisson@boundarydevices.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>