Revert "kbuild: Add option to turn incompatible pointer check into error"

This reverts commit ef50c04.

So adding -Werror=incompatible-pointer-types wasn't a bad idea, but it
should really not be done in the scheduler tree: it exposes us to a
number of pre-existing warnings (most of them harmless), now upgraded
to build failures...

This should be done via the kbuild tree.

Cc: Daniel Wagner <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: [email protected]
Cc: Boqun Feng <[email protected]>
Cc: Marcelo Tosatti <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: [email protected]

Author: Ingo Molnar

Makefile

@@ -773,9 +773,6 @@ KBUILD_CFLAGS   += $(call cc-option,-Werror=strict-prototypes)
 # Prohibit date/time macros, which would make the build non-deterministic
 KBUILD_CFLAGS   += $(call cc-option,-Werror=date-time)
 
-# enforce correct pointer usage
-KBUILD_CFLAGS   += $(call cc-option,-Werror=incompatible-pointer-types)
-
 # use the deterministic mode of AR if available
 KBUILD_ARFLAGS := $(call ar-option,D)