sunxi: clean up modules definitions

Module definitions for kmod-wdt-sunxi and kmod-eeprom-sunxi are removed
(wdt-sunxi was builtin anyways; nvmem-sunxi, which is the new name of
eeprom-sunxi is changed to builtin). As kmod-eeprom-sunxi was specified
in DEFAULT_PACKAGES, but not available on kernel 4.4, it was breaking the
image builder.

Support for kmod-sunxi-ir is added for kernel 4.4 (it is unclear why it
was disable before, it builds fine with with kernel 4.4).

Condtionals only relevant for pre-4.4 kernels are removed from modules.mk,
as sunxi does't support older kernels anymore.

Fixes FS#755.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>