mmsd: Use platform independent size types

Otherwise i386 builds are failing with -Werror-incompatible-pointer-types and
-Wformat.
8 jobs for fix-sizes in 11 minutes and 44 seconds
Status Name Job ID Coverage
  Build
passed build-pureos-gcc-byzantium #377050
librem5

00:01:50

passed build-pureos-gcc-byzantium-no-purple #377049
librem5

00:03:11

 
  Test
passed check-po #377052
librem5

00:00:15

passed test:debian-gcc #377051
librem5

00:03:22

19.0%
 
  Package
passed package-pureos-byzantium #377053
librem5

00:01:52

passed package-pureos-byzantium:arm64 #377054
librem5:arm64

00:05:09

 
  Test Package
passed autopkgtest-pureos-byzantium-package #377055
librem5

00:01:11

passed lintian-pureos-byzantium-package #377056
librem5

00:00:56