Add Keystone 2 DSP GPIO nodes for SoCs:
k2hk:
 DSP GPIO banks 0-7 correspond to DSP0-DSP7
k2l:
 DSP GPIO banks 0-3 correspond to DSP0-DSP3
k2e:
 DSP GPIO bank 0 corresponds to DSP0
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>