libgcc: Fix -Wint-conversion warning in find_fde_tail

Fixes commit r14-1614-g49310a99330849 ("libgcc: Fix eh_frame fast path
in find_fde_tail").

libgcc/

	PR libgcc/110179
	* unwind-dw2-fde-dip.c (find_fde_tail): Add cast to avoid
	implicit conversion of pointer value to integer.