bpf: optimize device type access away most of the time

bpf: optimize device type access away most of the time

Most of the time, we specify the allowed access mode as "rwm", so the check
always trivially passes. In that case, skip the check.

The repeating part changes from:
   5: (55) if r2 != 0x2 goto pc+6
   6: (bc) w1 = w3
   7: (54) w1 &= 7
   8: (5d) if r1 != r3 goto pc+3
   9: (55) if r4 != 0x1 goto pc+2
  10: (55) if r5 != 0x3 goto pc+1
  11: (05) goto pc+8
to
   6: (55) if r2 != 0x2 goto pc+3
   7: (55) if r4 != 0x1 goto pc+2
   8: (55) if r5 != 0x3 goto pc+1
   9: (05) goto pc+40