remove unnecessary SAM-specific code from NN-interface_cam.F90

[paogorman]

Remove nstep, nstatis, icycle, precsfc_i. These make sense in SAM but not CAM.

Remove duplicate setting of tabs0_sam=tabs_sam:

CAM-ML/src/physics/cam/nn_interface_cam.F90

Lines 189 to 193 in facd0ce

	tabs0_sam = tabs_sam
	!-----------------------------------------------------
	tabs0_sam = tabs_sam

[jatkinson1000]

This is addressed in #29 for review alongside other review updates.