Code clean up for wiring_analog

Replace hardcoded sensor 10 with TEMPSENSOR.
Indentation fixes
Fix timing of analogRead, divide clock by 5, and not by 6.

According to the comments in analogRead, we should take the 5MHz clock and
divide by 5. But currently, the code is dividing by 6.
This fix makes the clock be divided by 5.

ADC12DIV_0 is (0x0000) /* ADC12 Clock Divider Select: 0 */
..
ADC12DIV_4 is (0x0080) /* ADC12 Clock Divider Select: 4 */
ADC12DIV_5 is (0x00A0) /* ADC12 Clock Divider Select: 5 */
According to page 23 in http://www.ti.com/lit/ug/slau406b/slau406b.pdf,
this means we must use ADC12DIV_4 to divide by 5.
The code currently uses ADC12DIV_5, but this is dividing by 6.

The same is true for ADC10 :
ADC10DIV_0 is (0x0000) /* ADC10 Clock Divider Select: 0 */
..
ADC10DIV_4 is (0x0080) /* ADC10 Clock Divider Select: 4 */
ADC10DIV_5 is (0x00A0) /* ADC10 Clock Divider Select: 5 */
And according to page 18 in http://www.ti.com/lit/ug/slau315b/slau315b.pdf,
we must use ADC10DIV_4 to divide by 5, since ADC10DIV_5 is diving by 6.
Merge pull request #296 from alfh/master

Fix timing of analogRead for msp430, divide clock by 5, and not by 6