ACPICA: cast the result of the pointer difference to u32

Altnatively we could declare aml_length as acpi_size, but then one
would need to cast at the assignment for method_obj->method.aml_length

ACPICA commit 72805936603fcf84e98f1b89bf99b5101af27fb8

Link: https://github.com/acpica/acpica/commit/72805936
Signed-off-by: Sven Barth <sb@miray.de>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Erik Kaneda <erik.kaneda@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/nsxfname.c

@@ -516,7 +516,7 @@ acpi_status acpi_install_method(u8 *buffer)
 
 	method_flags = *parser_state.aml++;
 	aml_start = parser_state.aml;
-	aml_length = ACPI_PTR_DIFF(parser_state.pkg_end, aml_start);
+	aml_length = (u32)ACPI_PTR_DIFF(parser_state.pkg_end, aml_start);
 
 	/*
 	 * Allocate resources up-front. We don't want to have to delete a new