The OpenGL ES 3.0 spec states:
An INVALID_OPERATION error is generated if attachment is COLOR_-
ATTACHMENTm where m is greater than or equal to the value of MAX_COLOR_-
ATTACHMENTS.
An INVALID_ENUM error is generated if attachment is not one of the attachments
in table 4.6, and attachment is not COLOR_ATTACHMENTm where
m is greater than or equal to the value of MAX_COLOR_ATTACHMENTS.

Bug b/116776063

Change-Id: Iaabbcd3689d08ebdde2046440cf24554e9a160c2
Reviewed-on: https://swiftshader-review.googlesource.com/c/21908Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>