i965: Silence 'comparison is always true' warning

i965: Silence 'comparison is always true' warning

The parameter is an int16_t, and we're check that it's value will fit in
16-bits.  Yes, the value that is stored in 16-bits will surely fit in
16-bits.

brw_inst.h: In function 'brw_inst_set_gen6_jump_count':
brw_inst.h:321:66: warning: comparison is always true due to limited range of data type [-Wtype-limits]
brw_inst.h:321:66: warning: comparison is always true due to limited range of data type [-Wtype-limits]

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>