drm/i915: Fix compiler warnings for i915_edp_psr_status()

Appease both the poor reader and the compiler by rewriting the string
lookup for EDP_PSR2_STATUS_CTL:

drivers/gpu/drm/i915/i915_debugfs.c:2662 i915_edp_psr_status() warn: if statement not indented

Fixes: 6ba1f9e1

 ("drm/i915/psr: report live PSR2 State")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jim Bride <jim.bride@linux.intel.com>
Cc: Vathsala Nagaraju <vathsala.nagaraju@intel.com>
Cc: Patil Deepti <deepti.patil@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170116130622.20369-1-chris@chris-wilson.co.uk
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>