don't disable seeking after first seek failure

this could cause problems if the application uses dup2(fd,fileno(f))
to redirect, and the old fd was not seekable but the new fd is.

src/stdio/__stdio_seek.c

@@ -1,11 +1,5 @@
 #include "stdio_impl.h"
 
-static off_t retneg1(FILE *f, off_t off, int whence)
-{
-	errno = ESPIPE;
-	return -1;
-}
-
 off_t __stdio_seek(FILE *f, off_t off, int whence)
 {
 	off_t ret;
@@ -15,7 +9,5 @@ off_t __stdio_seek(FILE *f, off_t off, int whence)
 #else
 	ret = syscall(SYS_lseek, f->fd, off, whence);
 #endif
-	/* Detect unseekable files and optimize future failures out */
-	if (ret < 0 && errno == ESPIPE) f->seek = retneg1;
 	return ret;
 }