fix -Wformat issues reported by clang

[sebastienraillet]

Summary

This PR is about fixing compilation issues detected with clang on android 10 toolchain where -Werror and -Wformat are activated

Description

• some previous dlt_vlog was using %lu specifier to display an uint64_t variable. However, this isn't portable as depending on the system you're targeting (32bits, 64bits, Linux, android, etc.), the uint64_t can be an unsigned long long. This prevents compilation on system where -Werror and -Wformat is activated coupled with a less tolerant compiler (e.g clang). Instead, PRIxN macros (e.g PRIu64 for uint64_t) are now used as specifier to ensure compatibility for each platforms
• for bytes_read which is of type ssize_t, zd specifier is used as indicated in C99 standard
• for st_size (from struct stat) which is of type off_t, POSIX says that it should be a signed integer. To be safe, we now use %jd specifier to ensure that it will fit correctly