staging: kpc2000: Remove unnecessary return variable

staging: kpc2000: Remove unnecessary return variable

Remove unnecessary variable `val` in kp_spi_read_reg() that only holds
the return value from readq().
Issue found by coccinelle using the script:

@@
local idexpression ret;
expression e;
@@

-ret =
+return
     e;
-return ret;

Signed-off-by: Wambui Karuga <wambui.karugax@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Link: https://lore.kernel.org/r/20191009170703.GA2869@wambui
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>