Blackfin: Split the BF532 BFIN_*_FIO_FLAG() functions to their own header

Split the BF532 machine type BFIN_*_FIO_FLAG() functions to their own header
file to avoid circular #include problems as these functions require IRQ flag
handling, which requires asm/blackfin.h, which otherwise requires the header
file that defines these functions.

For good measure, also get rid of the inclusion of asm/blackfin.h from
mach/cdefBF532.h (which is circular) and defBF532.h (which is included by
asm/blackfin.h before including this header).

Signed-off-by: David Howells <dhowells@redhat.com>