Probe PCA953x successfully.

NOTE:

nsh> pca953x start
[PCA953X] on I2C bus 2 at 0x62
nsh> ls /dev
/dev:
 console
 led
 mmcsd0
 null
 pca
 ram0
 ttyS0
 ttyS1
 ttyS2

Signed-off-by: cctsao1008 <chiacheng.tsao@gmail.com>