HID: mcp2221: fix get and get_direction for gpio

The mcp2221_raw_event retrieves the value and direction of gpio on the
same command, by setting the value on mcp->status and the direction on
mcp->gpio_dir; and the offset at which they are read is based on
mcp->gp_idx, set by the gpiochip callbacks.

However, the individual gpiochip calls set the index to look for
directly on the field they want to track. This create a "double offset"
in the final read in the response report.

Align the behaviour of mcp2221_raw_event and
mcp_gpio_get/mcp_gpio_get_direction by putting gp_idx on those calls to
the base offset of the gpio status struct.

Signed-off-by: Louis Morhet <lmorhet@kalrayinc.com>
Link: https://lore.kernel.org/r/dd0b23800a79d2a464e1e9ed429b018b69fd5df2.1680602387.git.lmorhet@kalrayinc.com
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>

Author: Louis Morhet

drivers/hid/hid-mcp2221.c

@@ -594,7 +594,7 @@ static int mcp_gpio_get(struct gpio_chip *gc,
 
 	mcp->txbuf[0] = MCP2221_GPIO_GET;
 
-	mcp->gp_idx = offsetof(struct mcp_get_gpio, gpio[offset].value);
+	mcp->gp_idx = offsetof(struct mcp_get_gpio, gpio[offset]);
 
 	mutex_lock(&mcp->lock);
 	ret = mcp_send_data_req_status(mcp, mcp->txbuf, 1);
@@ -675,7 +675,7 @@ static int mcp_gpio_get_direction(struct gpio_chip *gc,
 
 	mcp->txbuf[0] = MCP2221_GPIO_GET;
 
-	mcp->gp_idx = offsetof(struct mcp_get_gpio, gpio[offset].direction);
+	mcp->gp_idx = offsetof(struct mcp_get_gpio, gpio[offset]);
 
 	mutex_lock(&mcp->lock);
 	ret = mcp_send_data_req_status(mcp, mcp->txbuf, 1);