kgdboc: fix return value of __setup handler

kgdboc: fix return value of __setup handler

BugLink: https://bugs.launchpad.net/bugs/1971497
[ Upstream commit ab818c7aa7544bf8d2dd4bdf68878b17a02eb332 ]

__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) environment strings.
So return 1 from kgdboc_option_setup().

Unknown kernel command line parameters "BOOT_IMAGE=/boot/bzImage-517rc7
  kgdboc=kbd kgdbts=", will be passed to user space.

 Run /sbin/init as init process
   with arguments:
     /sbin/init
   with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc7
     kgdboc=kbd
     kgdbts=

Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Fixes: 1bd54d851f50 ("kgdboc: Passing ekgdboc to command line causes panic")
Fixes: f2d937f3bf00 ("consoles: polling support, kgdboc")
Cc: He Zhe <zhe.he@windriver.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jiri Slaby <jirislaby@kernel.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Douglas Anderson <dianders@chromium.org>
Cc: linux-serial@vger.kernel.org
Reported-by: Igor Zhbanov <i.zhbanov@omprussia.ru>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20220309033018.17936-1-rdunlap@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>