Revert "RISC-V: mark hibernation as nonportable"

Revert commit ed309ce5 ("RISC-V: mark hibernation as nonportable")
as it appears the broken versions of OpenSBI have not made it to
production on any systems that support hibernation.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230802-chef-throng-d9de8b672a49@wendySigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/Kconfig

@@ -1011,11 +1011,8 @@ menu "Power management options"
 
 source "kernel/power/Kconfig"
 
-# Hibernation is only possible on systems where the SBI implementation has
-# marked its reserved memory as not accessible from, or does not run
-# from the same memory as, Linux
 config ARCH_HIBERNATION_POSSIBLE
-	def_bool NONPORTABLE
+	def_bool y
 
 config ARCH_HIBERNATION_HEADER
 	def_bool HIBERNATION