drm/i915: Fix spelling mistake in i915_reg.h

Fix typo: "TRIGER" --> "TRIGGER"

The two misplelled macros:

1) OAREPORTTRIG1_EDGE_LEVEL_TRIGER_SELECT_MASK
2) OAREPORTTRIG5_EDGE_LEVEL_TRIGER_SELECT_MASK

are not used in any other sources of the kernel,
so this change can be consider only a local change
for the i915_reg.h file.

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200703125046.8395-1-f.suligoi@asem.it