kernel: Remove macro definitions, pass variables using ccflags -y, and reapply manual su protection.

kernel: stop printing useless message unless its ddk environment
* In-tree build show empty KDIR

-- KDIR:
-- MDIR: /home/runner/work/KernelSU-Test/KernelSU-Test/kernel_414/KernelSU/kernel
  AR      drivers/iommu/built-in.o
  CC      drivers/input/misc/uinput.o
-- KernelSU version: 12329
-- KernelSU: CONFIG_KSU_MANUAL_HOOK
-- Supported KernelSU Manager(s): tiann, rsuntk, 5ec1cff
  CC      drivers/kernelsu/ksu.o
  AR      drivers/input/joystick/built-in.o
  CC      drivers/hid/hid-roccat-pyra.o

Co-authored-by: Faris <rissu.ntk@gmail.com>
Co-authored-by: ShirkNeko <109797057+ShirkNeko@users.noreply.github.com>

kernel/Kconfig

@@ -15,6 +15,13 @@ config KSU_DEBUG
     help
       Enable KernelSU debug mode.
 
+config KSU_MANUAL_SU
+    bool "Use manual su"
+    depends on KSU
+    default y
+    help
+      Use manual su and authorize the corresponding command line and application via prctl
+
 config KPM
     bool "Enable SukiSU KPM"
     depends on KSU && 64BIT