dtc: Sync with upstream commit 23387dd

[jlduran]

Summary

Add the ability to parse char literals needed to compile DTBs currently
in base.

Test Plan

TARGET=arm MACHINE=arm make builddtb FDT_DTS_FILE=stm32mp157c-ev1.dts

EDIT:
Since the import of Linux 6.5 device-tree sources, dts files are under a vendor-specific directory. Use the full path for now, so it can be found:

TARGET=arm MACHINE=arm make builddtb FDT_DTS_FILE=/usr/src/sys/contrib/device-tree/src/arm/st/stm32mp157c-ev1.dts