rockchip: rk3399: grf: Fix enum typos for UART2

rockchip: rk3399: grf: Fix enum typos for UART2

In the GRF header file, some instances of UART2 pinmux are prefixed with
"GRF_UART2DBG" while others have "GRF_UART2DGB".

Since UART2 is the default console UART and used for debugging, it is
more likely the name should be UART2DBG.

Fix the ones that are wrong.

Fixes: a2c08df3813b ("pinctrl: add driver for rk3399")
Fixes: fa72de10452c ("rockchip: arm64: rk3399: move grf register definitions to grf_rk3399.h")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Paul Kocialkowski <paulk@sys-base.io>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>