u-boot: v2026.04: fdt_fixup_ethernet: avoid nodeoff shadowing

When FDT_SEQ_MACADDR_FROM_ENV is defined, nodeoff is already declared
and assigned earlier in the function. The later 'int nodeoff = ...'
shadowed that variable and performed a redundant fdt_path_offset()
lookup.

Guard the inner declaration with #ifndef so it only exists when the
outer one does not. No behavior change — the same nodeoff value is
checked either way.

Addresses a CodeRabbit review comment on PR armbian#9675.

Author: iav

patch/u-boot/v2026.04/board_helios64/1001-fdt_fixup_ethernet-add-logs.patch

@@ -89,7 +89,9 @@ index 111111111111..222222222222 100644
  				continue;
 -
 +			}
++#ifndef FDT_SEQ_MACADDR_FROM_ENV
 +			int nodeoff = fdt_path_offset(fdt, path);
++#endif
 +			if (nodeoff < 0) {
 +				log_info("[fdt_fixup_ethernet] Node path '%s' not found, skipping\n", path);
 +				total_skipped++;