fix ath10k compile error

Author: amazingfate

backport-v6.1.39.patch

@@ -29735,7 +29735,7 @@ index 000000000..379387e20
 +F:	*/
 diff --git a/backports/Makefile b/backports/Makefile
 new file mode 100644
-index 000000000..3fecd5c54
+index 000000000..bc04254f2
 --- /dev/null
 +++ b/backports/Makefile
 @@ -0,0 +1,53 @@
@@ -29771,7 +29771,7 @@ index 000000000..3fecd5c54
 +	$(CFLAGS)
 +endif
 +
-+subdir-ccflags-y := $(call cc-option, -fno-pie) $(call cc-option, -no-pie)
++subdir-ccflags-y := $(call cc-option, -fno-pie) $(call cc-option, -no-pie)  -std=gnu11
 +ifeq ($(CONFIG_BACKPORT_KERNEL_4_3),y)
 +subdir-ccflags-y += -Wno-pointer-sign
 +endif