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@wambuiSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/kpc2000/kpc2000_spi.c

@@ -162,14 +162,12 @@ union kp_spi_ffctrl {
 kp_spi_read_reg(struct kp_spi_controller_state *cs, int idx)
 {
 	u64 __iomem *addr = cs->base;
-	u64 val;
 
 	addr += idx;
 	if ((idx == KP_SPI_REG_CONFIG) && (cs->conf_cache >= 0))
 		return cs->conf_cache;
 
-	val = readq(addr);
-	return val;
+	return readq(addr);
 }
 
 	static inline void