staging: sm750fb: Rename maxH to max_h in lynx_cursor

The struct lynx_cursor has a member named maxH. This name is
CamelCase and is frowned upon. This commit renames it to max_h
and makes the necessary changes for the module to build.

This change also fixes the following checkpatch CHECK:

CHECK: Avoid CamelCase: <maxH>
116: FILE: drivers/staging/sm750fb/sm750.c:116:
+           fbcursor->image.height > cursor->maxH ||

Signed-off-by: Benjamin Philip <benjamin.philip495@gmail.com>
Link: https://lore.kernel.org/r/692211000786d76aa41bc24d4ee06b5868d82771.1627304144.git.benjamin.philip495@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>