driver core: platform: Fix spelling errors in platform.c

There is a word spelling mistake of 'Unegisters', thus
it should be fixed.

Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20200520141202.19568-1-tangbin@cmss.chinamobile.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>