sysutils/dtc: fix clang 14 warning about use of bitwise logical operator

During an exp-run for llvm 14 (see bug 261742), it turned out that
sysutils/dtc fails to build with clang 14:

libfdt/fdt_rw.c:438:6: error: use of bitwise '|' with boolean operands [-Werror,-Wbitwise-instead-of-logical]

if (can_assume(LIBFDT_ORDER) |
    ^~~~~~~~~~~~~~~~~~~~~~~~~~
                             ||

libfdt/libfdt_internal.h:171:29: note: expanded from macro 'can_assume'

^

libfdt/fdt_rw.c:438:6: note: cast one or both operands to int to silence this warning
libfdt/libfdt_internal.h:171:29: note: expanded from macro 'can_assume'

^

This should have been a logical or instead. Upstream fixed this in:
https://github.com/dgibson/dtc/commit/7be250b4d059771c47be00ec8d4df7f47e4ac77c

PR: 261930
Approved by: maintainer timeout (2 weeks)
MFH: 2022Q1