arm64: dts: rockchip: Fix voltage threshold for volume keys for Pinephone Pro

arm64: dts: rockchip: Fix voltage threshold for volume keys for Pinephone Pro

Previously sometimes pressing the volume-down button would register as
a volume-up button. Match the thresholds as shown in the Pinephone Pro
schematic.

Tests:

~ $ evtest
    // Mashed the volume down ~100 times with varying intensity
    Event: time xxx, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 1
    Event: time xxx, type 1 (EV_KEY), code 114 (KEY_VOLUMEDOWN), value 0
    // Mashed the volume up ~100 times with varying intensity
    Event: time xxx, type 1 (EV_KEY), code 115 (KEY_VOLUMEUP), value 1
    Event: time xxx, type 1 (EV_KEY), code 115 (KEY_VOLUMEUP), value 0

Fixes: d3150ed53580 ("arm64: dts: rockchip: Add support for volume keys to rk3399-pinephone-pro")
Cc: stable@vger.kernel.org
Signed-off-by: Ondrej Jirman <megi@xff.cz>
Signed-off-by: Rudraksha Gupta <guptarud@gmail.com>
Reviewed-by: Pavel Machek <pavel@ucw.cz>
Link: https://patch.msgid.link/20251124-ppp_light_accel_mag_vol-down-v5-4-f9a10a0a50eb@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>