relax requirements in compiler SME capability check

cmake/system_check.cmake

@@ -142,7 +142,7 @@ endif()
 if (ARM64)
 if (NOT NO_SME)
   file(WRITE ${PROJECT_BINARY_DIR}/sme.c ".text \n.global sme_test\n\nsme_test:\nsmstart\nsmstop\nret\n")
-  execute_process(COMMAND ${CMAKE_C_COMPILER} -march=armv9-a+sve2+sme -c -v -o ${PROJECT_BINARY_DIR}/sme.o ${PROJECT_BINARY_DIR}/sme.c OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE NO_SME)
+  execute_process(COMMAND ${CMAKE_C_COMPILER} -march=armv8.4-a+sme -c -v -o ${PROJECT_BINARY_DIR}/sme.o ${PROJECT_BINARY_DIR}/sme.c OUTPUT_QUIET ERROR_QUIET RESULT_VARIABLE NO_SME)
 if (NO_SME EQUAL 1)
 set (CCOMMON_OPT "${CCOMMON_OPT} -DNO_SME")
 endif()