gas: dw2gencfi: reset reloc to TC_PARSE_CONS_RETURN_NONE for [su]leb128

Some consumers, like SFrame generation logic in GAS, may want to check
reloc value (without qualifying by e->type) as a part of their
admissibility criteria.  Setting reloc to TC_PARSE_CONS_RETURN_NONE for
these CFI escape expr nodes for [su]leb128 keeps the admissibility
checks simple and generic.

Previous discussion here:
https://sourceware.org/pipermail/binutils/2025-December/146807.html

gas/
	* gas/dw2gencfi.c (dot_cfi_escape): Set reloc to
	TC_PARSE_CONS_RETURN_NONE.