ARC: [plat-axs103] refactor the DT fudging code

ARC: [plat-axs103] refactor the DT fudging code

with clk frequency setting code gone by prev commits, we can elide the
unconditonal DT parsing to the specific case of quad core config where
we possibly need to fudge the DT value.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>