soc: mediatek: mtk-svs: fix passing zero to 'PTR_ERR'

nvmem_cell_get() cannot return NULL so checking for NULL is wrong here.

Signed-off-by: Roger Lu <roger.lu@mediatek.com>
Fixes: 6c7174fd90a4690 ("soc: mediatek: mtk-svs: use svs get efuse common function")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Link: https://lore.kernel.org/r/202302160720.N64SWT4l-lkp@intel.com/
Link: https://lore.kernel.org/r/20230216132543.814-1-roger.lu@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>