RISC-V: Add ACPI initialization in setup_arch()

Initialize the ACPI core for RISC-V during boot.

ACPI tables and interpreter are initialized based on
the information passed from the firmware and the value of
the kernel parameter 'acpi'.

With ACPI support added for RISC-V, the kernel parameter 'acpi'
is also supported on RISC-V. Hence, update the documentation.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230515054928.2079268-9-sunilvl@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/setup.c

@@ -8,6 +8,7 @@
  *  Nick Kossifidis <mick@ics.forth.gr>
  */
 
+#include <linux/acpi.h>
 #include <linux/cpu.h>
 #include <linux/init.h>
 #include <linux/mm.h>
@@ -276,6 +277,10 @@ void __init setup_arch(char **cmdline_p)
 
 	efi_init();
 	paging_init();
+
+	/* Parse the ACPI tables for possible boot-time configuration */
+	acpi_boot_table_init();
+
 #if IS_ENABLED(CONFIG_BUILTIN_DTB)
 	unflatten_and_copy_device_tree();
 #else