bpf, docs: Clarify call local offset

In the Jump instructions section it explains that the offset is
"relative to the instruction following the jump instruction".
But the program-local section confusingly said "referenced by
offset from the call instruction, similar to JA".

This patch updates that sentence with consistent wording, saying
it's relative to the instruction following the call instruction.
Signed-off-by: Dave Thaler <dthaler1968@gmail.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/20240525153332.21355-1-dthaler1968@gmail.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

Documentation/bpf/standardization/instruction-set.rst

@@ -552,9 +552,10 @@ is outside the scope of this document and is left for future work.
 Program-local functions
 ~~~~~~~~~~~~~~~~~~~~~~~
 Program-local functions are functions exposed by the same BPF program as the
-caller, and are referenced by offset from the call instruction, similar to
-``JA``.  The offset is encoded in the 'imm' field of the call instruction.
-An ``EXIT`` within the program-local function will return to the caller.
+caller, and are referenced by offset from the instruction following the call
+instruction, similar to ``JA``.  The offset is encoded in the 'imm' field of
+the call instruction. An ``EXIT`` within the program-local function will
+return to the caller.
 
 Load and store instructions
 ===========================