staging: iio: tsl2x7x_core: add spaces around operators

Address the checkpatch check by adding the necessary whitespace around
operators:

CHECK: spaces preferred around that '/' (ctx:VxV)

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