of: property: Increase NR_FWNODE_REFERENCE_ARGS

Currently, the following two macros have different values:

// The maximal argument count for firmware node reference
#define NR_FWNODE_REFERENCE_ARGS 8
// The maximal argument count for DT node reference
#define MAX_PHANDLE_ARGS 16

It may cause firmware node reference's argument count out of range if
directly assign DT node reference's argument count to firmware's.

drivers/of/property.c:of_fwnode_get_reference_args() is doing the direct
assignment, so may cause firmware's argument count @args->nargs got out
of range, namely, in [9, 16].

Fix by increasing NR_FWNODE_REFERENCE_ARGS to 16 to meet DT requirement.
Will align both macros later to avoid such inconsistency.

Fixes: 3e3119d3088f ("device property: Introduce fwnode_property_get_reference_args")
Signed-off-by: Zijun Hu <quic_zijuhu@quicinc.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Link: https://lore.kernel.org/r/20250225-fix_arg_count-v4-1-13cdc519eb31@quicinc.com
Signed-off-by: Rob Herring (Arm) <robh@kernel.org>