powerpc/pseries/bsr: Remove redundant initialization of bsr dev_t declaration.

Remove the unnecessary initialization of "dev_t bsr_dev" since it's
subsequently used in an "alloc_chrdev_region()" call which uses that
variable in an output-only fashion.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>