perf annotate: Fix a comment about multi_regs in extract_reg_offset function

perf annotate: Fix a comment about multi_regs in extract_reg_offset function

Fix a comment in function which explains how multi_regs field gets set
for an instruction. In the example, "mov  %rsi, 8(%rbx,%rcx,4)", the
comment mistakenly referred to "dst_multi_regs = 0". Correct it to use
"src_multi_regs = 0"

Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Akanksha J N <akanksha@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Disha Goel <disgoel@linux.vnet.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kajol Jain <kjain@linux.ibm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Segher Boessenkool <segher@kernel.crashing.org>
Link: https://lore.kernel.org/r/20240506121906.76639-4-atrajeev@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>