RT4334: Check UEFI before __STDC_VERSION__ for <inttypes.h>

Adding -nostdinc to the EDK2 showed that we were including <inttypes.h>
for some UEFI builds, because the check for __STDC_VERSION__ happens
before the check for OPENSSL_SYS_UEFI. Fix that.

Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Tim Hudson <tjh@openssl.org>