Set Clock Frequency for cocotb Sims to 800MHz

Set clock period default to 1.25ns for a frequency of 800MHz. This is
our target frequency.

Change-Id: I58cee127325b89bed4768496900a1bf8dfa2cc16

kelvin_test_utils/core_mini_axi_interface.py

diff --git a/kelvin_test_utils/core_mini_axi_interface.py b/kelvin_test_utils/core_mini_axi_interface.py
index 162e8b5..a217ecd 100644
--- a/kelvin_test_utils/core_mini_axi_interface.py
+++ b/kelvin_test_utils/core_mini_axi_interface.py
@@ -103,7 +103,7 @@
 
 
 class CoreMiniAxiInterface:
-  def __init__(self, dut):
+  def __init__(self, dut, clock_ns=1.25):
     self.dut = dut
     self.dut.io_aclk.value = 0
     self.dut.io_irq.value = 0
@@ -117,7 +117,7 @@
     self.dut.io_axi_slave_write_resp_ready.value = 0
     self.dut.io_axi_master_read_data_valid.value = 0
     self.dut.io_axi_master_write_resp_valid.value = 0
-    self.clock = Clock(dut.io_aclk, 10, unit="us")
+    self.clock = Clock(dut.io_aclk, clock_ns, unit="ns")
     self.memory_base_addr = 0x20000000
     self.memory = np.zeros([4 * 1024 * 1024], dtype=np.uint8)
     self.master_arfifo = Queue()