usdt: ignore location with incorrect probe virtual address
usdt: ignore location with incorrect probe virtual address

The patch fixed issue #1528. The linker ld.gold may generate
a probe with invalid virtual address if the section which the probe
relocates against is discarded.

Instead of failing, a simple checking is added such that
if the probe virtual address is less than the address of the first
instruction, print out a warning and ignore this probe.

Signed-off-by: Yonghong Song <e76892bbe783db2f627de1232e139db4de43da60@fb.com>

tuxology/bcc,iovisor/bcc,brendangregg/bcc,tuxology/bcc,tuxology/bcc,brendangregg/bcc,tuxology/bcc,iovisor/bcc,brendangregg/bcc,brendangregg/bcc,brendangregg/bcc,tuxology/bcc,mcaleavya/bcc,iovisor/bcc,mcaleavya/bcc,mcaleavya/bcc,iovisor/bcc,mcaleavya/bcc,mcaleavya/bcc,iovisor/bcc