greybus: es?: decrease buffer size to 2k

The firmware is having a hard time with 4k buffers and memory
allocation, so decrease the size on the host side to 2k.  Also move away
from using PAGE_SIZE to denote 4k as that's not the case on all
architectures, and someone, someday, might get a rude surprise.
Reviewed-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/es1.c

@@ -24,7 +24,7 @@
 
 /* Memory sizes for the buffers sent to/from the ES1 controller */
 #define ES1_SVC_MSG_SIZE	(sizeof(struct svc_msg) + SZ_64K)
-#define ES1_GBUF_MSG_SIZE_MAX	PAGE_SIZE
+#define ES1_GBUF_MSG_SIZE_MAX	2048
 
 static const struct usb_device_id id_table[] = {
 	/* Made up numbers for the SVC USB Bridge in ES1 */

drivers/staging/greybus/es2.c

@@ -24,7 +24,7 @@
 
 /* Memory sizes for the buffers sent to/from the ES1 controller */
 #define ES1_SVC_MSG_SIZE	(sizeof(struct svc_msg) + SZ_64K)
-#define ES1_GBUF_MSG_SIZE_MAX	PAGE_SIZE
+#define ES1_GBUF_MSG_SIZE_MAX	2048
 
 static const struct usb_device_id id_table[] = {
 	/* Made up numbers for the SVC USB Bridge in ES2 */