arch/riscv: Only initialize virtual memory if it's available

And do the detection just before the initialization.

Change-Id: I9a52430262f799baa298dc4f4ea459880abe250e
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/15831
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
1 file changed