drivers: tpm: atmel_twi: fix printf specifier compile warning

%d was being used as the specifier for size_t, leading to a
compiler warning

Signed-off-by: Mathew McBride <matt@traverse.com.au>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/drivers/tpm/tpm_atmel_twi.c b/drivers/tpm/tpm_atmel_twi.c
index a5dfb34..fa4fbec 100644
--- a/drivers/tpm/tpm_atmel_twi.c
+++ b/drivers/tpm/tpm_atmel_twi.c
@@ -116,7 +116,7 @@
 		}
 	}
 	if (res) {
-		printf("i2c_read returned %d (rlen=%d)\n", res, *recv_len);
+		printf("i2c_read returned %d (rlen=%zu)\n", res, *recv_len);
 #ifdef DEBUG
 		print_buffer(0, recvbuf, 1, *recv_len, 0);
 #endif