experimental st7567: Minor cleanup

[lhooge]

Hi,

two minor cleanups for the experimental st7567 device

• Fixes a comment for the CommonDirection
• Do not allocate unnecessary nulls for byte array

[codecov-io]

Codecov Report

Merging #453 (a5fe038) into master (19c7e6b) will increase coverage by 0.0%. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #453   +/-   ##
======================================
  Coverage    61.8%   61.8%           
======================================
  Files         126     126           
  Lines       11283   11282    -1     
======================================
  Hits         6973    6973           
+ Misses       4079    4078    -1     
  Partials      231     231           

Impacted Files	Coverage Δ
....io/x/periph/experimental/devices/st7567/st7567.go	0.0% <0.0%> (ø)

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[maruel]

Thanks!

[maruel]

gohci

[maruel]

Humm got flaky tests. They are unrelated to this CL.

[maruel]

Merged. Thanks again!