pata_cs5536: avoid implicit MSR API inclusion on x86-64

We don't need or want MSR usage here, on x86-64.
x86-64 was disabled intentionally in Kconfig, but commit
9272dcc2 changed that.

drivers/ata/pata_cs5536.c:47:1: warning: "rdmsr" redefined
In file included from arch/x86/include/asm/irqflags.h:60,
                 from include/linux/irqflags.h:15,
                 from arch/x86/include/asm/system.h:11,
                 from arch/x86/include/asm/processor.h:17,
                 from include/linux/prefetch.h:14,
                 from include/linux/list.h:7,
                 from include/linux/module.h:9,
                 from drivers/ata/pata_cs5536.c:33:
arch/x86/include/asm/paravirt.h:146:1: warning: this is the location of the previous definition
drivers/ata/pata_cs5536.c:48:1: warning: "wrmsr" redefined
arch/x86/include/asm/paravirt.h:154:1: warning: this is the location of the previous definition

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>