Do not use static_cast in C sources

C compiler does not recognise static_cast which is a C++ keyword
and bails out compiling mysys/my_rdtsc.c, use traditional typecast
instead

Upstream-Status: Submitted [https://github.com/MariaDB/server/pull/1981/files#r2032207090]
Signed-off-by: Khem Raj <raj.khem@gmail.com>
--- a/include/my_rdtsc.h
+++ b/include/my_rdtsc.h
@@ -226,7 +226,7 @@ static inline ulonglong my_timer_cycles(
         "sub %0, zero, %0\n"
         "and %1, %1, %0\n"
         : "=r"(result_hi0), "=r"(result_lo), "=r"(result_hi1));
-    return (static_cast<ulonglong>(result_hi1) << 32) | result_lo;
+    return ((ulonglong)result_hi1 << 32) | result_lo;
 # else
     ulonglong result;
     __asm __volatile__("rdtime %0" : "=r"(result));