test/py/tests: Update some network dependencies

On tests which require "tftpboot" we need to depend not on cmd_net but
rather cmd_tftpboot. And on tests which require cmd_pxe we do not need
to also depend on cmd_net as this should be handled already via Kconfig
logic.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/test/py/tests/test_net_boot.py b/test/py/tests/test_net_boot.py
index 4729ccf..63309fe 100644
--- a/test/py/tests/test_net_boot.py
+++ b/test/py/tests/test_net_boot.py
@@ -156,7 +156,7 @@
 
     return addr, timeout, pattern, chk_type, chk_pattern, config
 
-@pytest.mark.buildconfigspec('cmd_net')
+@pytest.mark.buildconfigspec('cmd_tftpboot')
 def test_net_tftpboot_boot(u_boot_console):
     """Boot the loaded image
 
@@ -209,7 +209,6 @@
 
     return f, bootfile
 
-@pytest.mark.buildconfigspec('cmd_net')
 @pytest.mark.buildconfigspec('cmd_pxe')
 def test_net_pxe_boot(u_boot_console):
     """Test the pxe boot command.
@@ -261,7 +260,6 @@
             u_boot_console.drain_console()
             u_boot_console.cleanup_spawn()
 
-@pytest.mark.buildconfigspec('cmd_net')
 @pytest.mark.buildconfigspec('cmd_pxe')
 def test_net_pxe_boot_config(u_boot_console):
     """Test the pxe boot command by selecting different combination of labels
@@ -341,7 +339,6 @@
             u_boot_console.drain_console()
             u_boot_console.cleanup_spawn()
 
-@pytest.mark.buildconfigspec('cmd_net')
 @pytest.mark.buildconfigspec('cmd_pxe')
 def test_net_pxe_boot_config_invalid(u_boot_console):
     """Test the pxe boot command by selecting invalid label