efi/libstub: Simplify "Exiting bootservices" message

The message

    "Exiting boot services and installing virtual address map...\n"

is even shown if we have efi=novamap on the command line or the firmware
does not provide EFI_RT_SUPPORTED_SET_VIRTUAL_ADDRESS_MAP.

To avoid confusion just print

    "Exiting boot services...\n"
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/libstub/fdt.c

@@ -271,7 +271,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(void *handle,
 		return status;
 	}
 
-	efi_info("Exiting boot services and installing virtual address map...\n");
+	efi_info("Exiting boot services...\n");
 
 	map.map = &memory_map;
 	status = efi_allocate_pages(MAX_FDT_SIZE, new_fdt_addr, ULONG_MAX);