regulator: cpr-regulator: add debugfs support for multiple devices

The cpr_enable module parameter is currently tied to a global
pointer, the_cpr, which corresponds to the last cpr-regulator
device probed.  This means that it is not possible to enable or
disable the CPR controller for the cpr-regulator devices that
probed first.

Remove the the_cpr pointer and the cpr_enable module parameter.
Replace them with a debugfs node for each cpr-regulator device
which can be used to enable and disable CPR individually.

Also fix the callback for the existing debug_info debugfs node
since it depends upon the_cpr.

New Debug Interface:

/sys/module/cpr_regulator/parameters/debug_enable
	Integer in which bit 0 enables kernel log messages
	generated when handling CPR interrupts and bit 1 enables
	other cpr-regulator log messages.  This parameter affects
	all cpr-regulator devices.

/sys/kernel/debug/regulator/<regulator-name>/cpr_enable
	Integer which controls whether or not CPR is enabled for
	a particular cpr-regulator device.  A value of 0
	corresponds to CPR disabled and a value of 1 corresponds
	to CPR enabled.  <regulator-name> corresponds to
	the name of the cpr-regulator device which is specified
	via the regulator-name device tree property.

/sys/kernel/debug/regulator/<regulator-name>/debug_info
	CPR status information for a particular cpr-regulator
	device.  <regulator-name> corresponds to the name of the
	cpr-regulator device which is specified via the
	regulator-name device tree property.

Old Debug Interface:

/sys/module/cpr_regulator/parameters/debug_enable
	Integer in which bit 0 enables kernel log messages
	generated when handling CPR interrupts and bit 1 enables
	other cpr-regulator log messages.  This parameter affects
	all cpr-regulator devices.

/sys/module/cpr_regulator/parameters/cpr_enable
	Integer which controls whether or not CPR is enabled for
	the last cpr-regulator device probed.  A value of 0
	corresponds to CPR disabled and a value of 1 corresponds
	to CPR enabled.  This parameter incorrectly does not
	control the CPR enable state for the first cpr-regulator
	devices probed.

/sys/kernel/debug/regulator/<regulator-name>/debug_info
	CPR status information for the last cpr-regulator device
	probed (regardless of which cpr-regulator device it seems
	to be associated with).  <regulator-name> corresponds to
	the name of the cpr-regulator device which is specified
	via the regulator-name device tree property.

Change-Id: I404ebdb3180f7dd9ae095867f7545d274be29e62
Signed-off-by: David Collins <collinsd@codeaurora.org>