soc: imx: gpcv2: Make use of regmap_read_poll_timeout()

Replace explicit polling loop with a call to
regmap_read_poll_timeout() to avoid code repetition. Also fix
misspelled "failed" while at it.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Chris Healy <cphealy@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>