__setup() handlers should return 1 to obsolete_checksetup() in
init/main.c to indicate that the boot option has been handled.
A return of 0 causes the boot option/value to be listed as an Unknown
kernel parameter and added to init's (limited) argument or environment
strings. Also, error return codes don't mean anything to
obsolete_checksetup() -- only non-zero (usually 1) or zero.
So return 1 from setup_kmac().

Fixes: 9e21c7e4 ("MIPS: RB532: Replace parse_mac_addr() with mac_pton().")
Fixes: 73b4390f ("[MIPS] Routerboard 532: Support for base system")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
From: Igor Zhbanov <i.zhbanov@omprussia.ru>
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Phil Sutter <n0-1@freewrt.org>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Daniel Walter <dwalter@google.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>