test/qtest/aspeed_smc-test: Move testcases to test_palmetto_bmc function

test/qtest/aspeed_smc-test: Move testcases to test_palmetto_bmc function

So far, the test cases are used for testing SMC model with AST2400 BMC.
However, AST2400 is end off live and ASPEED is no longer support this SOC.
To test SMC model for AST2500, AST2600 and AST1030, move the test cases
from main to test_palmetto_bmc function.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/r/20241127091543.1243114-2-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>