jep106: use packed jedec manufacturer code

jep106: use packed jedec manufacturer code

JEP106 encodes JEDEC-assigned manufacture code as:
a) a sequence of zero or more escape codes 0x7f;
b) an odd-parity bit of the next 7 bits;
c) 7 bits.

The same code is often represented as a single value composed by
the logical OR between:
- the number of escape codes in a), shifted left by 7 positions;
- the 7 bits in c).
This is the preferred packed representation used by this change.

Currently there are only two uses of JEP106 in openocd to get the
manufacturer name:
- to decode the JTAG IDCODE of each TAP, where the JEP106 code is
  already packed as in the preferred representation above in bits
  IDCODE[11:1];
- to decode the ARM CoreSight PIDR register, where the JEP106 code
  is split in 3 parts:
  = PIDR3[3:0], corresponding to bits [10:7] of the packed code;
  = PIDR2[2:0], corresponding to bits [6:4] of the packed code;
  = PIDR1[7:4], corresponding to bits [3:0] of the packed code.

Wrap the existing JEP106 decode function in a simpler API using
the packed code.
Simplify the callers by skipping the bit unpacking.
Change the manufacturer code in CoreSight table dap_partnums[] to
match the packed representation, by removing the always-one bit 7
erroneously taken from PIDR bit JEDEC and included in the former
table.

Change-Id: I63eb4da9e6801fab25e330f1f6b792d2fd619493
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/6418
Tested-by: jenkins