Use the smaller cgbase() macro in ufsread.c if UFS_SMALL_CGBASE is

defined.  This lets each boot program choose which version of cgbase() it
wants to use rather than forcing ufsread.c to have that knowledge.

MFC after:	1 week
Discussed with:	imp

sys/boot/arm/at91/boot2/boot2.c

@@ -93,6 +93,7 @@ static int parse(void);
 static int xfsread(ino_t, void *, size_t);
 static int dskread(void *, unsigned, unsigned);
 
+#define	UFS_SMALL_CGBASE
 #include "ufsread.c"
 
 static inline int

sys/boot/common/ufsread.c

@@ -48,10 +48,10 @@ __FBSDID("$FreeBSD$");
 
 #include <ufs/ufs/dinode.h>
 #include <ufs/ffs/fs.h>
-#if (defined(__i386__) && !defined(GPTBOOT)) || defined(__arm__)
+#ifdef UFS_SMALL_CGBASE
 /* XXX: Revert to old (broken for over 1.5Tb filesystems) version of cgbase
-   (see sys/ufs/ffs/fs.h rev 1.39) so that i386 boot loader (boot2) can
-   support both UFS1 and UFS2 again. */
+   (see sys/ufs/ffs/fs.h rev 1.39) so that small boot loaders (e.g. boot2) can
+   support both UFS1 and UFS2. */
 #undef cgbase
 #define cgbase(fs, c)   ((ufs2_daddr_t)((fs)->fs_fpg * (c)))
 #endif

sys/boot/i386/boot2/boot2.c

@@ -168,6 +168,7 @@ strcmp(const char *s1, const char *s2)
     return (unsigned char)*s1 - (unsigned char)*s2;
 }
 
+#define	UFS_SMALL_CGBASE
 #include "ufsread.c"
 
 static inline int

sys/boot/i386/gptboot/gptboot.c

@@ -167,7 +167,6 @@ strcmp(const char *s1, const char *s2)
     return (unsigned char)*s1 - (unsigned char)*s2;
 }
 
-#define GPTBOOT
 #include "ufsread.c"
 
 static inline int