Enable support for shmobile platforms that became multi-platform aware.
Several non-critical drivers and subsystems are built as modules, to keep
kernel size reasonable.

Tested on:
  - r8a73a4/ape6evm:
      - U-Boot fails with "Error: unrecognized/unsupported machine ID",
      - kexec works.
  - r8a7740/armadillo:
      - Hermit boot loader fails (larger image, more memory corruption),
      - kexec works.
  - r8a7791/koelsch,
  - sh73a0/kzm9g:
      - zImage+DTB from U-Boot needs CONFIG_ARM_ATAG_DTB_COMPAT=n,
      - kexec works.
  - am335x/boneblack.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>