gcc-7 warns about the result of a constant multiplication used as
a boolean:
drivers/ata/libata-core.c: In function 'ata_timing_quantize':
drivers/ata/libata-core.c:3164:30: warning: '*' in boolean context, suggest '&&' instead [-Wint-in-bool-context]
This slightly rearranges the macro to simplify the code and avoid
the warning at the same time.