drivers: hv: vmbus: Replace page definition with Hyper-V specific one

Replace PAGE_SIZE with HV_HYP_PAGE_SIZE because the guest page size may not
be 4096 on all architectures and Hyper-V always runs with a page size of
4096.
Signed-off-by: Maya Nakamura <m.maya.nakamura@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: Sasha Levin <sashal@kernel.org>
Link: https://lkml.kernel.org/r/0d9e80ecabcc950dc279fdd2e39bea4060123ba4.1562916939.git.m.maya.nakamura@gmail.com

drivers/hv/hyperv_vmbus.h

@@ -192,11 +192,11 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
 		       u64 *requestid, bool raw);
 
 /*
- * Maximum channels is determined by the size of the interrupt page
- * which is PAGE_SIZE. 1/2 of PAGE_SIZE is for send endpoint interrupt
- * and the other is receive endpoint interrupt
+ * The Maximum number of channels (16348) is determined by the size of the
+ * interrupt page, which is HV_HYP_PAGE_SIZE. 1/2 of HV_HYP_PAGE_SIZE is to
+ * send endpoint interrupts, and the other is to receive endpoint interrupts.
  */
-#define MAX_NUM_CHANNELS	((PAGE_SIZE >> 1) << 3)	/* 16348 channels */
+#define MAX_NUM_CHANNELS	((HV_HYP_PAGE_SIZE >> 1) << 3)
 
 /* The value here must be in multiple of 32 */
 /* TODO: Need to make this configurable */