riva_hw.c: Ensure ABS macro expands correctly
Handles warning from Oracle Parfait 11.2 static analyser:
Error: Misleading macro
Misleading macro [misleading-macro]:
misleading evaluation of unary '-' operator in expansion of macro ABS due to missing parentheses
at line 104 of src/riva_hw.c.
binary '+' operator has lower precedence than unary '-' operator inside macro body at line 298
if (ABS(ainfo->vburst_size) + (ABS(ainfo->wcvlwm + 32) & ~0xf) - tmp> VFIFO_SIZE)
low precedence binary '+' operator is hidden by expansion of macro argument a at line 104
#define ABS(a) (a>0?a:-a)