PTP: Declare 'static' some variables

PTP: Declare 'static' some variables

Fix warnings given by '-Wmissing-variable-declarations':

./print-ptp.c:262:13: warning: no previous extern declaration for
non-static variable 'p_porigin_ts' [-Wmissing-variable-declarations]
const char *p_porigin_ts = "preciseOriginTimeStamp";
            ^
./print-ptp.c:262:7: note: declare 'static' if the variable is not
intended to be used outside of this translation unit
const char *p_porigin_ts = "preciseOriginTimeStamp";
      ^
./print-ptp.c:263:13: warning: no previous extern declaration for
non-static variable 'p_origin_ts' [-Wmissing-variable-declarations]
const char *p_origin_ts = "originTimeStamp";
            ^
./print-ptp.c:263:7: note: declare 'static' if the variable is not
intended to be used outside of this translation unit
const char *p_origin_ts = "originTimeStamp";
      ^
./print-ptp.c:264:13: warning: no previous extern declaration for
non-static variable 'p_recv_ts' [-Wmissing-variable-declarations]
const char *p_recv_ts = "receiveTimeStamp";
            ^
./print-ptp.c:264:7: note: declare 'static' if the variable is not
intended to be used outside of this translation unit
const char *p_recv_ts = "receiveTimeStamp";

Moreover:
Put a function definition name at the beginning of the line.