u-boot: Upgrade to 2016.03 release

u-boot: Upgrade to 2016.03 release

The 2016.03 release has been announced in March 14th. This
incorporates a lot of bug fixes and improvements which are useful for
any new embedded development.

Along with the upgrade of U-Boot and its related recipes, this patch
also drops the AM335x environment fix which has been merged into the
release.

(From OE-Core rev: 15130f7bad0f0a1894c34bbb34a547722552c69e)

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>