nvmem: core: Add stub for nvmem_cell_read_u8

Add the stub nvmem_cell_read_u8() function for drivers running with
CONFIG_NVMEM disabled.
Signed-off-by: Komal Bajaj <quic_kbajaj@quicinc.com>
Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com>
Link: https://lore.kernel.org/r/20230830105654.28057-4-quic_kbajaj@quicinc.comSigned-off-by: Bjorn Andersson <andersson@kernel.org>

include/linux/nvmem-consumer.h

@@ -127,6 +127,12 @@ static inline int nvmem_cell_write(struct nvmem_cell *cell,
 	return -EOPNOTSUPP;
 }
 
+static inline int nvmem_cell_read_u8(struct device *dev,
+				     const char *cell_id, u8 *val)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int nvmem_cell_read_u16(struct device *dev,
 				      const char *cell_id, u16 *val)
 {