isapnp: BKL removal

Remove BKL use from isapnp_proc_bus_lseek(), like was done for
proc_bus_pci_lseek() a long time ago and recently for Zorro
by Geert Uytterhoeven.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Jaroslav Kysela <perex@perex.cz>