Remove templating from QuadUVMatrix::apply, and fix const-ness

The function is inlined - the compiler can do whatever optimizations it
wants at each call-site. In the future, stride and uvOffset won't be
static (with optional wide colors), so this is required anyway.

Also, the pointer being passed in is never const, so stop cleverly
casting away the const-ness via reinterpret into and out of intptr_t.

Bug: skia:
Change-Id: I404c418a01d70ac77667ba89338940b086922dc6
Reviewed-on: https://skia-review.googlesource.com/c/179988
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
4 files changed