[XFS] Fix char size overflow in bmap_alloc call for unwritten extent

conversion.

Since bma.conv is a char and XFS_BMAPI_CONVERT is 0x1000, bma.conv was
always assigned zero. Spotted by the GNU C compiler (SVN version).

SGI-PV: 947312
SGI-Modid: xfs-linux-melb:xfs-kern:26887a
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NNathan Scott <nathans@sgi.com>

fs/xfs/xfs_bmap.c

@@ -4993,7 +4993,7 @@ xfs_bmapi(
 				bma.firstblock = *firstblock;
 				bma.alen = alen;
 				bma.off = aoff;
-				bma.conv = (flags & XFS_BMAPI_CONVERT);
+				bma.conv = !!(flags & XFS_BMAPI_CONVERT);
 				bma.wasdel = wasdelay;
 				bma.minlen = minlen;
 				bma.low = flist->xbf_low;