bpf: Handle i32 for ALU operations without ISA support

There is no eBPF ISA support for BSWAP, ROTR, ROTL, SREM, SDIVREM, MULHU,
ADDC, ADDE etc on i32.

They could be emulated by other basic BPF_ALU operations, we'd set their
lowering action the same as i64.

Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Reviewed-by: Yonghong Song <yhs@fb.com>
llvm-svn: 325984