STATIC_ASSERT is #define'd to a compiler specific value, based on
built-in macros exposed by those compilers. If none of those are found,
an #error is raised.
This breaks the DTCPP build rule, which relies on the C preprocessor
for header file inclusion and value substitution, but doesn't define any
of the compiler macros we look for.
So drop the error case. If STATIC_ASSERT is used without a definition,
an error will be raised anyway.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>