powerpc/pseries: Add spaces around / operator

This is follow up change after 14b5d59a ("powerpc/pseries: Fix
formatting to make code look more beautiful") to conform to kernel
coding style.

Signed-off-by: Petr Vaněk <arkamar@atlas.cz>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230324220041.11378-1-arkamar@atlas.cz