kbuild: force to define __UBOOT__ in all the C sources

U-Boot has imported various source files from other projects,
mostly Linux.

Something like

  #ifdef __UBOOT__
    [ modification for U-Boot ]
  #else
    [ original code ]
  #endif

is an often used strategy for clarification of adjusted parts,
that is, easier re-sync in future.

Instead of defining __UBOOT__ in each source file,
passing it from the top Makefile would be easier.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Heiko Schocher <hs@denx.de>

include/linux/mtd/flashchip.h

@@ -9,7 +9,6 @@
 #ifndef __MTD_FLASHCHIP_H__
 #define __MTD_FLASHCHIP_H__
 
-#define __UBOOT__
 #ifndef __UBOOT__
 /* For spinlocks. sched.h includes spinlock.h from whichever directory it
  * happens to be in - so we don't have to care whether we're on 2.2, which

include/linux/mtd/mtd.h

@@ -8,7 +8,6 @@
 #ifndef __MTD_MTD_H__
 #define __MTD_MTD_H__
 
-#define __UBOOT__
 #ifndef __UBOOT__
 #include <linux/types.h>
 #include <linux/uio.h>

include/linux/mtd/nand.h

@@ -16,7 +16,6 @@
 #ifndef __LINUX_MTD_NAND_H
 #define __LINUX_MTD_NAND_H
 
-#define __UBOOT__
 #ifndef __UBOOT__
 #include <linux/wait.h>
 #include <linux/spinlock.h>

include/linux/mtd/ubi.h

@@ -10,7 +10,6 @@
 #define __LINUX_UBI_H__
 
 #include <linux/types.h>
-#define __UBOOT__
 #ifndef __UBOOT__
 #include <linux/ioctl.h>
 #include <mtd/ubi-user.h>