uml: use correct type in BLKGETSIZE ioctl

I found a type mismatch in UML that makes host block devices unusable as ubd
devices on x86_64 and other 64 bits systems (segfault of the mm subsystem):

In block/ioctl.c, the following lines show that the BLKGETSIZE ioctl expects
a pointer to a long:

	case BLKGETSIZE:
		if ((bdev->bd_inode->i_size >> 9) > ~0UL)
			return -EFBIG;
		return put_ulong(arg, bdev->bd_inode->i_size >> 9);

In arch/um/os-Linux/file.c, os_file_size calls it with an int.

The ioctl_list man page should be fixed as well.

Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/um/os-Linux/file.c

@@ -320,7 +320,8 @@ int os_file_size(char *file, unsigned long long *size_out)
 	}
 
 	if(S_ISBLK(buf.ust_mode)){
-		int fd, blocks;
+		int fd;
+		long blocks;
 
 		fd = os_open_file(file, of_read(OPENFLAGS()), 0);
 		if(fd < 0){