kernel: guard functionality that requires kprobes

Since upstream is now making kprobes a requirement, we adapt this tree to still allow
building with manual hooks in an easier way. Furthermore, this also allows a user to
build with manual hooks even with kprobes enabled.

Offending commit:
	kernel: remove unused CONFIG guard becuase GKI kernel enable kprobe by default
	upstream: https://github.com/tiann/KernelSU/commit/500ff9b

Other changes:
	ksud.c, stop_input_hook(), short-circuit redundant logic left by this change.
	cherry pick from: https://github.com/backslashxx/KernelSU/commit/a3d3e93

Signed-off-by: backslashxx <118538522+backslashxx@users.noreply.github.com>

kernel/Kconfig

@@ -9,6 +9,14 @@ config KSU
 	  To compile as a module, choose M here: the
 	  module will be called kernelsu.
 
+config KSU_WITH_KPROBES
+	bool "Use kprobes for kernelsu"
+	depends on KSU
+	depends on KPROBES
+	default y
+	help
+	  Disable if you use manual hooks.
+
 config KSU_DEBUG
 	bool "KernelSU debug mode"
 	depends on KSU