dtc: update to 1.7.2

dtc: update to 1.7.2

Changelog:
- 2d10aa2 Bump version to v1.7.2
- 48795c8 pylibfdt: Don't emit warnings from swig generate C code
- 838f11e fdtoverlay: provide better error message for missing `/__symbols__`
- d1e2384 pylibfdt/libfdt.i: Use SWIG_AppendOutput
- 18aa49a Escape spaces in depfile with backslashes.
- f9968fa libfdt.h: whitespace consistency fixups
- 9b5f65f libfdt.h: typo and consistency fixes

Link: https://github.com/openwrt/openwrt/pull/20858
Signed-off-by: Nick Hainke <[email protected]>