Cleanup patch from Hollis Blanchard <hollis@austin.ibm.com>

We have a large number of private implementations of BIN_TO_BCD and
BCD_TO_BIN, which are all the same.  And a lot of them are inflexible because
they modify their arg:

	#define BIN_TO_BCD(val) ((val)=(((val)/10)<<4) + (val)%10)

- Create (in <linux/bcd.h> a generic BIN2BCD/BCD2BIN which does not modify
  its arg

- Create generic BIN_TO_BCD/BCD_TO_BIN which uses the above

- Update lots of callers to use the new generic version.