Removed a conversion to integer which was removing all subpixel
precision from coordinates when using clampToEdge.

Passes all out of bounds cases (this cl should only affect these cases).

Fixes:
dEQP-GLES3.functional.fbo.blit.default_framebuffer.srgb8_alpha8_linear_out_of_bounds_blit_from_default

Change-Id: Id7cef212ea2b739ef22148779dbc1228628e4440
Reviewed-on: https://swiftshader-review.googlesource.com/15988Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>