octeon: switch to Kernel 5.15 by default

Getting ready for the next release.

Signed-off-by: Paul Spooren <[email protected]>

target/linux/octeon/Makefile

@@ -10,8 +10,7 @@ BOARDNAME:=Cavium Networks Octeon
 FEATURES:=squashfs ramdisk pci usb
 CPU_TYPE:=octeonplus
 
-KERNEL_PATCHVER:=5.10
-KERNEL_TESTING_PATCHVER:=5.15
+KERNEL_PATCHVER:=5.15
 
 define Target/Description
 	Build firmware images for Cavium Networks Octeon-based boards.