ARM: omap2plus_defconfig: reduce zImage size on omap2plus_defconfig

By converting a few drivers to modules because they
won't be needed during boot anyways, we can shave off
about 700KiB of text.

Note that while at that, and after discussions with Tony
Lindgren, a few extra drivers were either removed because
they weren't needed, or added because they're useful for
debugging/testing.

Below is output of size for pre and post vmlinux binaries:

   text    data     bss     dec     hex filename
8514799  765532 8416064 17696395        10e068b vmlinux-post-patch
9069110  800316 8419072 18288498        1170f72 vmlinux-pre-patch

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>