x86/acpi: simplify updating header checksum

Use acpi_update_checksum() for updating ACPI table header checksum.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Matthias Brugger <mbrugger@suse.com>
diff --git a/arch/x86/cpu/apollolake/hostbridge.c b/arch/x86/cpu/apollolake/hostbridge.c
index 039236d..284f16c 100644
--- a/arch/x86/cpu/apollolake/hostbridge.c
+++ b/arch/x86/cpu/apollolake/hostbridge.c
@@ -298,7 +298,7 @@
 
 	/* (Re)calculate length and checksum */
 	header->length = ctx->current - (void *)dmar;
-	header->checksum = table_compute_checksum((void *)dmar, header->length);
+	acpi_update_checksum(header);
 
 	acpi_align(ctx);
 	acpi_add_table(ctx, dmar);