math/slatec: Unbreak build with GCC 10

Error: Rank mismatch between actual argument at (1) and actual argument at (2) (rank-1 and scalar)
cpzero.f:90:43:

76 |       CALL CPEVL(N,N,A,TEMP,T,T,.FALSE.)
   |                            2

......

90 |          CALL CPEVL(N,0,T(N1),CMPLX(X,0.0),PN,PN,.FALSE.)
   |                                           1

Error: Rank mismatch between actual argument at (1) and actual argument at (2) (rank-1 and scalar)
cpzero.f:105:37:

76 |       CALL CPEVL(N,N,A,TEMP,T,T,.FALSE.)
   |                            2

......

105 |                CALL CPEVL(N,0,A,R(I),PN,TEMP,.TRUE.)
    |                                     1

Error: Rank mismatch between actual argument at (1) and actual argument at (2) (rank-1 and scalar)

http://package18.nyi.freebsd.org/data/121amd64-default-PR244494/2020-06-10_18h04m44s/logs/errors/slatec-4.1_12.log

PR: 246700