Merge tag 'arc-fixes-for-2019.04-rc1' of git://git.denx.de/u-boot-arc

A couple of trivial fixes and improvements for ARC

Most notable are:
 * Move of ENV_SIZE/ENV_OFFSET to Kconfig
 * Fix with private structure allocation for arc_uart
 * Definition of CONFIG_SYS_CACHELINE_SIZE useful for building drivers