ext2fs: fix warning: 'blocknxt' may be used uninitialized with gcc 4.2

The above warning was introduced originally in 436da3cd "ext2load:
increase read speed" and fixed for newer toolchains in b8032734 "ext2fs:
fix warning: 'blocknxt' may be used uninitialized".  This change did not
fix the warning with gcc 4.2, as found in ELDK 4.2.

If we rework the while loop to initalize blocknxt before entering the
warning really goes away.  Tested on am335x with an approx 7mb file and
crc32 in U-Boot befor and after this change.

Cc: Wolfgang Denk <wd@denx.de>
Cc: Eric Nelson <eric.nelson@boundarydevices.com>
Cc: Thierry Reding <thierry.reding@avionic-design.de>
Cc: Jason Cooper <u-boot@lakedaemon.net>
Cc: Andreas Bießmann <andreas.devel@googlemail.com>
Cc: Reinhard Arlt <reinhard.arlt@esd-electronics.com>
Cc: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Tom Rini <trini@ti.com>

fs/ext2/ext2fs.c

@@ -440,9 +440,8 @@ int ext2fs_read_file
 		/* grab middle blocks in one go */
 		if (i != pos / blocksize && i < blockcnt - 1 && blockcnt > 3) {
 			int oldblk = blknr;
-			int blocknxt;
+			int blocknxt = ext2fs_read_block(node, i + 1);
 			while (i < blockcnt - 1) {
-				blocknxt = ext2fs_read_block(node, i + 1);
 				if (blocknxt == (oldblk + 1)) {
 					oldblk = blocknxt;
 					i++;
@@ -450,6 +449,7 @@ int ext2fs_read_file
 					blocknxt = ext2fs_read_block(node, i);
 					break;
 				}
+				blocknxt = ext2fs_read_block(node, i);
 			}
 
 			if (oldblk == blknr)