linux: disable -Werror

Disable -Werror to fix the following build failure with esp-hosted
raised at least since commit a382a7d55432918d2a1e47ae4cbe7ed50fa17a08:

In function ‘destroy_cmd_wq’,
    inlined from ‘esp_commands_teardown’ at /home/autobuild/autobuild/instance-4/output-1/build/esp-hosted-ce3c50a33fa4bc562a1b6cbcee292c1ae0b0a404/esp_hosted_ng/host/esp_cmd.c:1467:2:
./include/linux/workqueue.h:639:9: error: call to ‘__warn_flushing_systemwide_wq’ declared with attribute warning: Please avoid flushing system-wide workqueues. [-Werror=attribute-warning]
  639 |         __warn_flushing_systemwide_wq();                                \
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/autobuild/autobuild/instance-4/output-1/build/esp-hosted-ce3c50a33fa4bc562a1b6cbcee292c1ae0b0a404/esp_hosted_ng/host/esp_cmd.c:408:17: note: in expansion of macro ‘flush_scheduled_work’
  408 |                 flush_scheduled_work();
      |                 ^~~~~~~~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.org/results/6ac7a4601938d3296ed1657c06f8cdf433757d73
 - http://autobuild.buildroot.org/results/7997cc8a67645a6e1cf4e24d172c6feae459dcfb

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
(cherry picked from commit 6b56e0b4f09b36140e2cb9e41072d5ac6074f375)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

linux/linux.mk

@@ -436,6 +436,7 @@ define LINUX_KCONFIG_FIXUP_CMDS
 		$(call KCONFIG_ENABLE_OPT,CONFIG_LOGO)
 		$(call KCONFIG_ENABLE_OPT,CONFIG_LOGO_LINUX_CLUT224))
 	$(call KCONFIG_DISABLE_OPT,CONFIG_GCC_PLUGINS)
+	$(call KCONFIG_DISABLE_OPT,CONFIG_WERROR)
 	$(PACKAGES_LINUX_CONFIG_FIXUPS)
 endef