misc: genwqe: Constify struct pci_error_handlers

misc: genwqe: Constify struct pci_error_handlers

genwqe_err_handler is never modified, so it can be made const to allow
the compiler to put it in read-only memory.

Before:
   text    data     bss     dec     hex filename
  20174    6104    2464   28742    7046 drivers/misc/genwqe/card_base.o

After:
   text    data     bss     dec     hex filename
  20270    6008    2464   28742    7046 drivers/misc/genwqe/card_base.o

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20200610224704.27082-3-rikard.falkeborn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>