i386: Change prefetchi output template

i386: Change prefetchi output template

For prefetchi instructions, RIP-relative address is explicitly mentioned
for operand and assembler obeys that rule strictly. This makes
instruction like:

	prefetchit0	bar

got illegal for assembler, which should be a broad usage for prefetchi.

Change to %a to explicitly add (%rip) after function label to make it
legal in assembler so that it could pass to linker to get the real address.

gcc/ChangeLog:

	* config/i386/i386.md (prefetchi): Change to %a.

gcc/testsuite/ChangeLog:

	* gcc.target/i386/prefetchi-1.c: Check (%rip).