posix: device_io: require a full libc for c89 functions

The POSIX_DEVICE_IO Option Group requires a number of c89
functions mainly from stdio.h .

Namely,

clearerr(), fclose(), feof(), ferror(), fflush(), fetc(),
fgets(), fprintf(), fputc(), fputs(), fread(), freopen(),
fscanf(), fwrite(), getc(), getchar(), gets(), perror(),
printf(), putc(), putchar(), puts(), scanf(), setbuf(),
setvbuf(), ungetc(), vfprintf(), vfscanf(), vfprintf(), and
vscanf().

These should be provided by any conformant C library
(not by the POSIX API).

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>