Patch merged into coreboot/master: riscv: Stub out sbi_(un)mask_interrupt

the following patch was just integrated into master:
commit 522dcd1249d577c1828cb49f6cd300bc11c6f914
Author: Jonathan Neuschäfer 
Date:   Thu Nov 24 08:10:13 2016 +0100

riscv: Stub out sbi_(un)mask_interrupt

Linux needs these SBI calls, but so far it seems to work when they don't
    do anything.

Change-Id: I2cd0bb3ab91e89805fed84ec87e4a48ce70c3a46
    Signed-off-by: Jonathan Neuschäfer 
    Reviewed-on: https://review.coreboot.org/17593
    Tested-by: build bot (Jenkins)
    Reviewed-by: Ronald G. Minnich

See https://review.coreboot.org/17593 for details.

-gerrit