pinctrl: aspeed: Fix GPI only function problem.

Some gpio pin at aspeed soc is input only and the prefix name of these
pin is "GPI" only.
This patch fine-tune the condition of GPIO check from "GPIO" to "GPI"
and it will fix the usage error of banks D and E in the AST2400/AST2500
and banks T and U in the AST2600.

Fixes: 4d3d0e4 ("pinctrl: Add core support for Aspeed SoCs")
Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Link: https://lore.kernel.org/r/20201030055450.29613-1-billy_tsai@aspeedtech.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/aspeed/pinctrl-aspeed.c

@@ -286,13 +286,14 @@ int aspeed_pinmux_set_mux(struct pinctrl_dev *pctldev, unsigned int function,
 static bool aspeed_expr_is_gpio(const struct aspeed_sig_expr *expr)
 {
 	/*
-	 * The signal type is GPIO if the signal name has "GPIO" as a prefix.
+	 * The signal type is GPIO if the signal name has "GPI" as a prefix.
 	 * strncmp (rather than strcmp) is used to implement the prefix
 	 * requirement.
 	 *
-	 * expr->signal might look like "GPIOT3" in the GPIO case.
+	 * expr->signal might look like "GPIOB1" in the GPIO case.
+	 * expr->signal might look like "GPIT0" in the GPI case.
 	 */
-	return strncmp(expr->signal, "GPIO", 4) == 0;
+	return strncmp(expr->signal, "GPI", 3) == 0;
 }
 
 static bool aspeed_gpio_in_exprs(const struct aspeed_sig_expr **exprs)