pci: fix type warnings in intr_remapping.c

pci: fix type warnings in intr_remapping.c

Commit 69309a059075 ("x86, asm: Clean up and simplify set_64bit()")
sanitized the x86-64 types to set_64bit(), and incidentally resulted in
warnings like

 drivers/pci/intr_remapping.c: In function 'modify_irte':
 drivers/pci/intr_remapping.c:314: warning: passing argument 1 of 'set_64bit' from incompatible pointer type
 arch/x86/include/asm/cmpxchg_64.h:6: note:expected 'volatile u64 *' but argument is of type 'long unsigned int *'

It turns out that the change to set_64bit() really does clean up things,
and the PCI intr_remapping.c file did a rather ugly cast in order to
avoid warnings with the previous set_64bit() type model.

Removing the ugly cast fixes the warning, and makes everybody happy and
expects a set_64bit() to take the logical "u64 *" argument.

Pointed-out-by: Peter Anvin <hpa@zytor.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>