of/fdt: Check fdt_get_mem_rsv() error in early_init_fdt_scan_reserved_mem()

early_init_fdt_scan_reserved_mem() invoks fdt_get_mem_rsv(), and it will
use uninitialized variables @base and @size once the callee suffers error.

Fix by checking fdt_get_mem_rsv() error as other callers do.

Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Link: https://lore.kernel.org/r/20250109-of_core_fix-v4-13-db8a72415b8c@quicinc.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>