pistachio: use kernel 6.12 by default

Switch to Linux kernel version 6.12.

Signed-off-by: Zoltan HERPAI <[email protected]>

target/linux/pistachio/Makefile

@@ -12,8 +12,7 @@ CPU_TYPE:=24kc
 CPU_SUBTYPE:=24kf
 SUBTARGETS:=generic
 
-KERNEL_PATCHVER:=6.6
-KERNEL_TESTING_PATCHVER:=6.12
+KERNEL_PATCHVER:=6.12
 
 include $(INCLUDE_DIR)/target.mk