refactor(xilinx): create generic function for clock retrieval

Refactors the code in the AMD-Xilinx platform for Versal and Versal NET
to create a more generic function for obtaining clock signals
from the platform. The new function  get_uart_clk is specific to each
platform and providing greater flexibility for clock signal retrieval
in various parts of the codebase.

Signed-off-by: Prasad Kummari <prasad.kummari@amd.com>
Change-Id: Iff67315339b2651c9bea73af0d89fcbad2bb332a
diff --git a/plat/xilinx/versal_net/include/plat_private.h b/plat/xilinx/versal_net/include/plat_private.h
index be75bfd..3eb8052 100644
--- a/plat/xilinx/versal_net/include/plat_private.h
+++ b/plat/xilinx/versal_net/include/plat_private.h
@@ -18,6 +18,7 @@
 } versal_intr_info_type_el3_t;
 
 void versal_net_config_setup(void);
+uint32_t get_uart_clk(void);
 
 const mmap_region_t *plat_versal_net_get_mmap(void);