kernel: split kernel version to dedicated files

Move the kernel versions and hash to dedicated files.
This makes kernel bump quicker and fix some annoying
problem with rebasing when multiple kernel bump are proposed.

Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
[Rebased on top of current master]
Signed-off-by: Rui Salvaterra <rsalvaterra@gmail.com>

include/kernel-5.10

+LINUX_VERSION-5.10 = .90
+LINUX_KERNEL_HASH-5.10.90 = 945e4264c014a3d9dfc0a4639309dd1ec2fb545416556421f931b95da78c2725

include/kernel-5.4

+LINUX_VERSION-5.4 = .170
+LINUX_KERNEL_HASH-5.4.170 = b09f74e0cf5fc7cf5de6aa932fe654c962cb10118bdbbdddb397022c6e6d382c

include/kernel-version.mk

@@ -6,11 +6,12 @@ ifdef CONFIG_TESTING_KERNEL
   KERNEL_PATCHVER:=$(KERNEL_TESTING_PATCHVER)
 endif
 
-LINUX_VERSION-5.4 = .170
-LINUX_VERSION-5.10 = .90
+KERNEL_DETAILS_FILE=$(INCLUDE_DIR)/kernel-$(KERNEL_PATCHVER)
+ifeq ($(wildcard $(KERNEL_DETAILS_FILE)),)
+  $(error Missing kernel version/hash file for $(KERNEL_PATCHVER). Please create $(KERNEL_DETAILS_FILE))
+endif
 
-LINUX_KERNEL_HASH-5.4.170 = b09f74e0cf5fc7cf5de6aa932fe654c962cb10118bdbbdddb397022c6e6d382c
-LINUX_KERNEL_HASH-5.10.90 = 945e4264c014a3d9dfc0a4639309dd1ec2fb545416556421f931b95da78c2725
+include $(KERNEL_DETAILS_FILE)
 
 remove_uri_prefix=$(subst git://,,$(subst http://,,$(subst https://,,$(1))))
 sanitize_uri=$(call qstrip,$(subst @,_,$(subst :,_,$(subst .,_,$(subst -,_,$(subst /,_,$(1)))))))