LinuxKPI: Implement _ioremap_attr for riscv

Now that riscv implements pmap_mapdev_attr we can enable the non-stub
implementation for riscv, which is needed for drm-kmod to not fail at
run time for drivers that need to map I/O regions.

Reviewed by:	hselasky, bz
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D32446

(cherry picked from commit 60d962e)

sys/compat/linuxkpi/common/include/linux/io.h

@@ -390,7 +390,7 @@ _outb(u_char data, u_int port)
 }
 #endif
 
-#if defined(__i386__) || defined(__amd64__) || defined(__powerpc__) || defined(__aarch64__)
+#if defined(__i386__) || defined(__amd64__) || defined(__powerpc__) || defined(__aarch64__) || defined(__riscv)
 void *_ioremap_attr(vm_paddr_t phys_addr, unsigned long size, int attr);
 #else
 #define	_ioremap_attr(...) NULL

sys/compat/linuxkpi/common/src/linux_compat.c

@@ -1822,7 +1822,7 @@ vmmap_remove(void *addr)
 	return (vmmap);
 }
 
-#if defined(__i386__) || defined(__amd64__) || defined(__powerpc__) || defined(__aarch64__)
+#if defined(__i386__) || defined(__amd64__) || defined(__powerpc__) || defined(__aarch64__) || defined(__riscv)
 void *
 _ioremap_attr(vm_paddr_t phys_addr, unsigned long size, int attr)
 {
@@ -1845,7 +1845,7 @@ iounmap(void *addr)
 	vmmap = vmmap_remove(addr);
 	if (vmmap == NULL)
 		return;
-#if defined(__i386__) || defined(__amd64__) || defined(__powerpc__) || defined(__aarch64__)
+#if defined(__i386__) || defined(__amd64__) || defined(__powerpc__) || defined(__aarch64__) || defined(__riscv)
 	pmap_unmapdev((vm_offset_t)addr, vmmap->vm_size);
 #endif
 	kfree(vmmap);