i965: Delete pitch alignment assertion in get_blit_intratile_offset_el.

i965: Delete pitch alignment assertion in get_blit_intratile_offset_el.

The cacheline alignment restriction is on the base address; the pitch
can be anything.

Fixes assertion failures when using primus (say, on glxgears, which
creates a 300x300 linear BGRX surface with a pitch of 1200):

intel_blit.c:190: get_blit_intratile_offset_el: Assertion `mt->surf.row_pitch % 64 == 0' failed.

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>