gpio: slg7xl45106: Update gpio desc flags from DT

In current slg7xl45106 gpio driver xlate() function we are not updating
gpio flags from DT. Read the given flag from DT and update the gpio desc
flags variable with required gpio direction state.

Signed-off-by: T Karthik Reddy <t.karthik.reddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Link: https://lore.kernel.org/r/a8d7b4799337bd99f61ace509889f02b192a9414.1648631275.git.michal.simek@xilinx.com