drm/i915/lobf: Add debug interface for lobf

drm/i915/lobf: Add debug interface for lobf

Add an interface in debugfs which will help in debugging LOBF
feature.

v1: Initial version.
v2:
- Remove FORCE_EN flag. [Jouni]
- Change prefix from I915 to INTEL. [Jani]
- Use u8 instead of bool for lobf-debug flag. [Jani]
v3:
- Use intel_connector instead of display. [Jani]
- Remove edp connector check as it was already present
in caller function. [Jani]
- Remove loop of searching edp encoder which is directly
accessible from intel_connector. [Jani]
v4:
- Simplify alpm debug to bool instead of bit-mask. [Jani]
v5:
- Remove READ_ONCE(). [Jani]
- Modify variable name to *_disable_*. [Jouni]
v6: Improved debug print. [Jouni]

Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>
Link: https://lore.kernel.org/r/20250423092334.2294483-8-animesh.manna@intel.com