stm32mp: bsec: add check on null size in misc ops

Add a protection in misc bsec ops for request with null size.

For example OP-TEE error occurs when get_eth_nb() return 0 in
setup_mac_address() for unknown part number because U-Boot read 0 OTPs.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/arch/arm/mach-stm32mp/bsec.c b/arch/arm/mach-stm32mp/bsec.c
index f5f4b20..0dc1e5c 100644
--- a/arch/arm/mach-stm32mp/bsec.c
+++ b/arch/arm/mach-stm32mp/bsec.c
@@ -622,7 +622,7 @@
 		shadow = false;
 	}
 
-	if ((offs % 4) || (size % 4))
+	if ((offs % 4) || (size % 4) || !size)
 		return -EINVAL;
 
 	if (IS_ENABLED(CONFIG_OPTEE) && priv->tee) {
@@ -678,7 +678,7 @@
 		shadow = false;
 	}
 
-	if ((offs % 4) || (size % 4))
+	if ((offs % 4) || (size % 4) || !size)
 		return -EINVAL;
 
 	if (IS_ENABLED(CONFIG_OPTEE) && priv->tee) {