zephyr: use cmsis_core.h header

CMSIS glue code is now provided by the CMSIS Zephyr module in
<cmsis_core.h>. Header is generic for M/A/R.

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>
diff --git a/boot/zephyr/main.c b/boot/zephyr/main.c
index d8d4cff..8551649 100644
--- a/boot/zephyr/main.c
+++ b/boot/zephyr/main.c
@@ -27,11 +27,7 @@
 #include <soc.h>
 #include <zephyr/linker/linker-defs.h>
 
-#if defined(CONFIG_CPU_AARCH32_CORTEX_A) || defined(CONFIG_CPU_AARCH32_CORTEX_R)
-#include <zephyr/arch/arm/aarch32/cortex_a_r/cmsis.h>
-#elif defined(CONFIG_CPU_CORTEX_M)
-#include <zephyr/arch/arm/aarch32/cortex_m/cmsis.h>
-#endif
+#include <cmsis_core.h>
 
 #include "target.h"