bpf, docs: Fix typo "BFP_ALU" to "BPF_ALU"

"BFP" should be "BPF"
Signed-off-by: Kosuke Fujimoto <fujimotokosuke0@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220609083937.245749-1-fujimotoksouke0@gmail.com

Documentation/bpf/instruction-set.rst

@@ -127,7 +127,7 @@ BPF_XOR | BPF_K | BPF_ALU64 means::
 Byte swap instructions
 ----------------------
 
-The byte swap instructions use an instruction class of ``BFP_ALU`` and a 4-bit
+The byte swap instructions use an instruction class of ``BPF_ALU`` and a 4-bit
 code field of ``BPF_END``.
 
 The byte swap instructions operate on the destination register