Make media support modular to reduce kernel size (-253 KiB):

       text    data     bss     dec     hex   filename
    12451039 1396476  339800 14187315  d87b33 vmlinux.before
    12202692 1387244  338456 13928392  d487c8 vmlinux.after
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>