stm32mp1: update test on misc_read result

Update the stm32mp1 baord after the commit 8729b1ae2cbd
("misc: Update read() and write() methods to return bytes xfered")

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/board/st/stm32mp1/stm32mp1.c b/board/st/stm32mp1/stm32mp1.c
index 654c489..d994d38 100644
--- a/board/st/stm32mp1/stm32mp1.c
+++ b/board/st/stm32mp1/stm32mp1.c
@@ -103,7 +103,7 @@
 	if (!ret)
 		ret = misc_read(dev, STM32_BSEC_SHADOW(BSEC_OTP_BOARD),
 				&otp, sizeof(otp));
-	if (!ret && otp) {
+	if (ret > 0 && otp) {
 		printf("Board: MB%04x Var%d Rev.%c-%02d\n",
 		       otp >> 16,
 		       (otp >> 12) & 0xF,