dtc(1): Update to 1a79f5f26631

Highlights:

• Bugfix for order in which /delete-node/ and /delete-property/ are processed [0]
• /omit-if-no-ref/ support has been added (used only by U-Boot at this point, in theory)
• GPL dtc compat version bumped to 1.4.7
• Various small fixes and compatibility improvements

Reported by: strejda [0]
MFC after: 1 week