cmake: add the gcc -mcpu parameter value for the Cortex-A9 CPU

Add the -mcpu=cortex-a9 option as part of the basic aarch32 Cortex-A
CPU support.

Signed-off-by: Immo Birnbaum <Immo.Birnbaum@weidmueller.com>

cmake/gcc-m-cpu.cmake

diff --git a/cmake/gcc-m-cpu.cmake b/cmake/gcc-m-cpu.cmake
index 2ced557..45a2351 100644
--- a/cmake/gcc-m-cpu.cmake
+++ b/cmake/gcc-m-cpu.cmake
@@ -40,6 +40,8 @@
     set(GCC_M_CPU cortex-r5)
   elseif(CONFIG_CPU_CORTEX_R7)
     set(GCC_M_CPU cortex-r7)
+  elseif(CONFIG_CPU_CORTEX_A9)
+    set(GCC_M_CPU cortex-a9)
   else()
     message(FATAL_ERROR "Expected CONFIG_CPU_CORTEX_x to be defined")
   endif()