mfd: ab8500-debugfs: Trivially beautify the debugfs driver

Just lots of white space corrections, changing some of the 4 space
tabs to 8 and pulling back some of the double tabbing back into
singles, such as the remaining of the driver.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Samuel Ortiz <sameo@linux.intel.com>