staging: iio: tsl2x7x_core: add blank line after struct declaration

Add the missing blank line after struct declaration. Checkpatch found
this issue.

CHECK: Please use a blank line after function/struct/union/enum
declarations

Signed-off-by: Eva Rachel Retuya <eraretuya@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>