arch/riscv: Delegate the page fault exceptions

These exceptions were new in the Privileged Architecture spec 1.10.
We need to delegate them to S-mode.

Change-Id: Iec15afe9656107b9aeea1677c5b8dc7d654fa746
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/23774
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>

src/arch/riscv/virtual_memory.c

@@ -32,6 +32,9 @@ static int delegate = 0
 	| (1 << CAUSE_LOAD_ACCESS)
 	| (1 << CAUSE_STORE_ACCESS)
 	| (1 << CAUSE_USER_ECALL)
+	| (1 << CAUSE_FETCH_PAGE_FAULT)
+	| (1 << CAUSE_LOAD_PAGE_FAULT)
+	| (1 << CAUSE_STORE_PAGE_FAULT)
 	;
 
 void mstatus_init(void)