ARM: imx: cpuidle-imx6sx: Restrict the SW2ISO increase to i.MX6SX

commit b25af2ff7c07bd19af74e3f64ff82e2880d13d81 upstream.

Since commit 1e434b703248 ("ARM: imx: update the cpu power up timing
setting on i.mx6sx") some characters loss is noticed on i.MX6ULL UART
as reported by Christoph Niedermaier.

The intention of such commit was to increase the SW2ISO field for i.MX6SX
only, but since cpuidle-imx6sx is also used on i.MX6UL/i.MX6ULL this caused
unintended side effects on other SoCs.

Fix this problem by keeping the original SW2ISO value for i.MX6UL/i.MX6ULL
and only increase SW2ISO in the i.MX6SX case.

Cc: stable@vger.kernel.org
Fixes: 1e434b703248 ("ARM: imx: update the cpu power up timing setting on i.mx6sx")
Reported-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Tested-by: Christoph Niedermaier <cniedermaier@dh-electronics.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>