ANDROID: Move BRANCH/KMI_GENERATION from build.config.common to .constants.

We are deprecating build.config.common so we have
one less build config for build-config-less builds. Even though the
value of `BRANCH` and `KMI_GENERATION` is technically not needed in
Bazel's analysis phase,
we still move it back to build.config.constants so we have a central
place to put branch-specific variables.

Bug: 276493276
Bug: 236012223
Change-Id: I0d63399af44e2a4da379fa224f4e53e25052207a
Signed-off-by: HONG Yifan <elsk@google.com>

build.config.common

@@ -1,7 +1,3 @@
 . ${ROOT_DIR}/${KERNEL_DIR}/build.config.constants
 
-KMI_GENERATION=0
-
-BRANCH=android16-6.12
-
 KCFLAGS="${KCFLAGS} -D__ANDROID_COMMON_KERNEL__"

build.config.constants

@@ -1,3 +1,5 @@
+BRANCH=android16-6.12
+KMI_GENERATION=0
 CLANG_VERSION=r536225
 RUSTC_VERSION=1.82.0
 AARCH64_NDK_TRIPLE=aarch64-linux-android31