riscv: change payload() to pass the config string pointer as arg0

The riscv 1.9 standard defines a textual config string to be passed
to kernels and hypervisors. Change the payload function to pass
this string in a0.

Change-Id: I3be7f1712accf2d726704e4c970f22749d3c3f36
Signed-off-by: Ronald G. Minnich <rminnich@gmail.com>
Reviewed-on: https://review.coreboot.org/17254
Tested-by: build bot (Jenkins)
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
1 file changed