bpf, docs: Fix typos in instructions-set.rst

* "imm32" should just be "imm"
* Add blank line to fix formatting error reported by Stephen Rothwell [0]

[0]: https://lore.kernel.org/bpf/[e-mail]/T/#u

Signed-off-by: Dave Thaler <[e-mail]>
Acked-by: David Vernet <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

Documentation/bpf/standardization/instruction-set.rst

···
 instruction has one or more conformance groups of which it is a member.
 
 This document defines the following conformance groups:
+
 * base32: includes all instructions defined in this
   specification unless otherwise noted.
 * base64: includes base32, plus instructions explicitly noted
···
 
 ``BPF_XOR | BPF_K | BPF_ALU`` means::
 
-  dst = (u32) dst ^ (u32) imm32
+  dst = (u32) dst ^ (u32) imm
 
 ``BPF_XOR | BPF_K | BPF_ALU64`` means::
 
-  dst = dst ^ imm32
+  dst = dst ^ imm
 
 Note that most instructions have instruction offset of 0. Only three instructions
 (``BPF_SDIV``, ``BPF_SMOD``, ``BPF_MOVSX``) have a non-zero offset.
···
 
 ``BPF_MEM | <size> | BPF_ST`` means::
 
-  *(size *) (dst + offset) = imm32
+  *(size *) (dst + offset) = imm
 
 ``BPF_MEM | <size> | BPF_LDX`` means::