src/eccd.f90: remove caching functionality from eccdeff

The caching is cool, but it's implemented using static variables and
therefore not thread-safe. Since the savings are pretty modest (about
20% of the total eccdeff calls, itself 3% of the total execution) let's
just drop it.

src/eccd.f90

@@ -718,7 +718,6 @@ contains
 ! sfd(1),...,sfd(4) - coefficients of the polynomial expansion of the 
 !                 "Spitzer"-function (the same as in the Hirshman paper)
 !=======================================================================
-    use const_and_precisions, only : mc2_
     IMPLICIT NONE
     REAL(wp_), INTENT(in) :: mu,Zeff,fc
     INTEGER   :: n,i,j
@@ -732,22 +731,6 @@ contains
                        alp23,alp24,alp20, &
                              alp34,alp30,alp40
     REAL(wp_) :: bet0,bet1,bet2,bet3,bet4,d0
-    LOGICAL   :: renew,rel,newmu,newZ,newfc
-    REAL(wp_), SAVE :: sfdx(1:4) = 0
-    REAL(wp_), SAVE :: mu_old =-1, Zeff_old =-1, fc_old =-1
-
-    rel   = mu < mc2_
-    newmu = abs(mu  -mu_old  ) > delta*mu
-    newZ  = abs(Zeff-Zeff_old) > delta*Zeff
-    newfc = abs(fc  -fc_old  ) > delta*fc
-    SELECT CASE(adj_appr(1))
-    CASE ('l','c')
-      renew = (newmu .and. rel) .OR. newZ .OR. newfc
-    END SELECT
-    IF (.not.renew) THEN
-      sfd(:) = sfdx(:)
-      RETURN
-    ENDIF
 
     tn(:) = 0
     IF (adj_appr(4) == 'r') THEN
@@ -839,11 +822,6 @@ contains
     sfd(2) = bet2-alp20*d0-alp24*sfd(4)-alp23*sfd(3)
     sfd(1) = bet1-alp10*d0-alp14*sfd(4)-alp13*sfd(3)-alp12*sfd(2)
 
-    fc_old   = fc
-    mu_old   = mu
-    Zeff_old = Zeff
-    sfdx(1:4) = sfd(1:4)
-
   END SUBROUTINE SpitzFuncCoeff
 
   SUBROUTINE SpitzFunc_HighSpeedLimit(Zeff,fc,u,q,gam, K,dKdu)