ARM: dts: am43xx: Remove wrongly defined RSTST offset for PER Domain

As per the TRM: http://www.ti.com/lit/ug/spruh73m/spruh73m.pdf


offset 0x4 is reserved for PRM_PER. Hence removing the wrongly
defined address offset.

Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>