rtc: m48t59: remove redundant pointer 'name'

Pointer 'name' is being assigned but is never used hence it is redundant
and can be removed.

Cleans up clang warning:
warning: variable 'name' set but not used [-Wunused-but-set-variable]

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>