soc: imx7d: fix CPP application building error

For CPP application, such as samples/cpp/cpp_synchronization/, it will
report the following building errors:

...
zephyrproject/modules/hal/nxp/imx/devices/MCIMX7D/./MCIMX7D_M4.h:5101:51:
error: 'reinterpret_cast<CCM_Type*>(808976384)' is not a constant
expression
...

The error is caused by commit: 72312fee
" arch: arm: cortex_m: Use cmsis api instead of inline asm in arch_irq_*"
This patch will cause kernel.h includes cmsis_core.h which includes soc.h,
so that soc.h will be used by c++ code.

This patch make soc.h can be c++ compatible.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>