ARM: dts: bcm2835: fix uart0/uart1 pins

According to the BCM2835 ARM Peripherals document uart1 doesn't map to pins
36-39, but uart0 does.

Also, split into separate Rx/Tx and CST/RTS groups to match other uart nodes.

Fixes: 21ff8439 ("ARM: dts: bcm283x: Define standard pinctrl groups in the gpio node.")
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Eric Anholt <eric@anholt.net>