nvmem: stm32: add warning when upper OTPs are updated

nvmem: stm32: add warning when upper OTPs are updated

As the upper OTPs are ECC protected, they support only one 32 bits word
programming.
For a second modification of this word, these ECC become invalid and
this OTP will be no more accessible, the shadowed value is invalid.

This patch adds a warning to indicate an upper OTP update, because this
operation is dangerous as OTP is not locked by the driver after the first
update to avoid a second update.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221118063932.6418-3-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>