pinctrl: aspeed: Fix GPI only function problem.

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: 4d3d0e4272d8 ("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>