kernel: fix support for sparc64

[fingolfin]

Thanks to Bill Allombert for reporting this and providing an earlier version of this change.

[codecov]

Codecov Report

Merging #1124 into master will increase coverage by <.01%.

@@            Coverage Diff             @@
##           master    #1124      +/-   ##
==========================================
+ Coverage   57.06%   57.07%   +<.01%     
==========================================
  Files         433      433              
  Lines      224712   224712              
==========================================
+ Hits       128222   128244      +22     
+ Misses      96490    96468      -22

Impacted Files	Coverage Δ
lib/polyrat.gi	58.71% <ø> (-0.76%)	❌
lib/factgrp.gi	83.36% <ø> (+0.2%)	✅
lib/stbcrand.gi	90.36% <ø> (+0.39%)	✅
lib/straight.gi	25.69% <ø> (+0.41%)	✅
lib/grpmat.gi	71.45% <ø> (+0.55%)	✅
lib/tietze.gi	42.91% <ø> (+0.73%)	✅

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[ChrisJefferson]

I tried this patch on my sparc VM and it seemed to fix the problem. I will merge unless anyone comments shortly.