Fixed NetBSD memory and uptime

[polluks]

before

\\`-______,----__     polluks@sdf
 \\        __,---`_   os     NetBSD 9.1
  \\       `.____     host   amd64
   \\-______,----`-   uptime 19143d 13h 42m
    \\                memory -7765M / 0M
     \\
      \\

after

\\`-______,----__     polluks@sdf
 \\        __,---`_   os     NetBSD 9.1
  \\       `.____     host   amd64
   \\-______,----`-   uptime 19143d 13h 45m
    \\                memory 8611M / 16382M
     \\
      \\

815c815
<             mem_full=$(($(sysctl -n hw.physmem64 || echo 0) / 1024 / 1024))
---
>             mem_full=$(($(/sbin/sysctl -n hw.physmem64 || echo 0) / 1024 / 1024))

[polluks]

BTW uptime 52 years?! My patch

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