Merge tag 'efi-2019-04-rc4-3' of https://github.com/xypron2/u-boot

Pull request for UEFI system for v2019.04-rc4

Fix an error with the serial communication on boards with a very small
UART buffer which leads to a stalled system.

Provide an X86 reset driver for the UEFI runtime.

Fix a problem with parallel builds.