input: qti-haptics: Fix the variable type for getting element size

While parsing per effect properties, element size is obtained
as u32 data type which converts the negative value like -EINVAL
to a large value and fails parsing the property. Fix it by using
"int" data type.

Change-Id: Ifd64495e4cd810f12be61268f2eb9c6174ceede7
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>