ARM: net: bpf: improve 64-bit ALU implementation

Improbe the 64-bit ALU implementation from:

  movw    r8, #65532
  movt    r8, #65535
  movw    r9, #65535
  movt    r9, #65535
  ldr     r7, [fp, #-44]
  adds    r7, r7, r8
  str     r7, [fp, #-44]
  ldr     r7, [fp, #-40]
  adc     r7, r7, r9
  str     r7, [fp, #-40]

to:

  movw    r8, #65532
  movt    r8, #65535
  movw    r9, #65535
  movt    r9, #65535
  ldrd    r6, [fp, #-44]
  adds    r6, r6, r8
  adc     r7, r7, r9
  strd    r6, [fp, #-44]

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>