kernel: Use CONFIG_KSU=m to compile lkm (#1468)

before:
CONFIG_KSU=y
CONFIG_KSU_MODULE=y

after:
CONFIG_KSU=m

---------

Signed-off-by: dabao1955 <dabao1955@163.com>
Co-authored-by: weishu <twsxtd@gmail.com>

kernel/Kconfig

@@ -5,20 +5,15 @@ config KSU
 	depends on OVERLAY_FS
 	default y
 	help
-	Enable kernel-level root privileges on Android System.
+	  Enable kernel-level root privileges on Android System.
+	  To compile as a module, choose M here: the
+	  module will be called kernelsu.
 
 config KSU_DEBUG
 	bool "KernelSU debug mode"
 	depends on KSU
 	default n
 	help
-	Enable KernelSU debug mode
-
-config KSU_MODULE
-	bool "Build KernelSU as a module"
-	depends on KSU
-	default n
-	help
-	Build KernelSU as a loadable kernel module
+	  Enable KernelSU debug mode.
 
 endmenu

kernel/Makefile

@@ -16,11 +16,7 @@ kernelsu-objs += selinux/rules.o
 ccflags-y += -I$(srctree)/security/selinux -I$(srctree)/security/selinux/include
 ccflags-y += -I$(objtree)/security/selinux -include $(srctree)/include/uapi/asm-generic/errno.h
 
-ifndef KSU_MODULE
-obj-y += kernelsu.o
-else
-obj-m += kernelsu.o
-endif
+obj-$(CONFIG_KSU) += kernelsu.o
 
 # .git is a text file while the module is imported by 'git submodule add'.
 ifeq ($(shell test -e $(srctree)/$(src)/../.git; echo $$?),0)