net: ipa: add new most-significant bits to registers

IPA v4.5 adds a few fields to the endpoint header and extended
header configuration registers that represent new high-order bits
for certain offsets and sizes.  Add code to incorporate these upper
bits into the registers for IPA v4.5.

This includes creating ipa_header_size_encoded(), which handles
encoding the metadata offset field for use in the ENDP_INIT_HDR
register in a way appropriate for the hardware version.  This and
ipa_metadata_offset_encoded() ensure the mask argument passed to
u32_encode_bits() is constant.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>