nvmem: check the return value of nvmem_add_cells()

nvmem: check the return value of nvmem_add_cells()

BugLink: https://bugs.launchpad.net/bugs/1836802
[ Upstream commit fa72d847d68d7833b77a4bef944cf2c5baf56f49 ]

This function can fail so check its return value in nvmem_register()
and act accordingly.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>