The 8051 assembler sign-extends every value to 24 bits, so the top
byte of a __sfr32 address list like 0xa4a5a6a7 comes out as 0xff.
The patch keeps 32-bit arithmetic while leaving the 24-bit T line
addresses alone, so the relocations are unchanged. Proposed upstream
in the bug thread. With it SFR_DATA_U32 can be used again, which
saves about 240 bytes of code in REG_SET.
