rcu: avoid literal suffix warning in C++ mode

rcu: avoid literal suffix warning in C++ mode

Sequences like "value = %"PRIu64 (no space before PRIu64) are parsed as
a single preprocessor token, user-defined-string-literal, in C++11
onwards. While modern compilers are smart enough to parse this properly,
GCC 9.3.0 generates warnings like:

    rte_rcu_qsbr.h:555:26: warning: invalid suffix on literal; C++11
    requires a space between literal and string macro [-Wliteral-suffix]

Add spaces around format specifier macros to make public headers
compatible with C++ without causing warnings. Make similar changes in C
source for style consistency within the library.

Fixes: 64994b56c ("rcu: add RCU library supporting QSBR mechanism")
Cc: stable@dpdk.org
Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>