ghash-armv4.pl: excuse myself from implementing "528B" flavour.

# loop, this assembler loop body was found to be ~3x smaller than

# compiler-generated one...

#

# Note about "528B" variant. In ARM case it makes lesser sense to

# implement it for following reasons:

#

# - performance improvement won't be anywhere near 50%, because 128-

#   bit shift operation is neatly fused with 128-bit xor here, and

#   "538B" variant would eliminate only 4-5 instructions out of 32

#   in the inner loop (meaning that estimated improvement is ~15%);

# - ARM-based systems are often embedded ones and extra memory

#   consumption might be unappreciated (for so little improvement);

#

# Byte order [in]dependence. =========================================

#

# Caller is expected to maintain specific *dword* order in Htable,