cmd: bcb: Use strcmp() instead of strncmp() for string literals

cmd: bcb: Use strcmp() instead of strncmp() for string literals

Quote from https://patchwork.ozlabs.org/patch/1104244/#2210814:

 ----------8<-----------
strncmp() is chosen for the sake of paranoid/defensive programming.
Indeed, strncmp() is not really needed when comparing a variable
with a string literal. We expect strcmp() to behave safely even if the
string variable is not NUL-terminated.

In the same scenario, Linux v5.2-rc7 uses both strcmp() and strncmp(),
but the frequency of strcmp() is higher:

$ git --version
git version 2.22.0
$ (Linux 5.2-rc7) git grep -En 'strncmp\([^"]*"[[:alnum:]]+"' | wc -l
1066
$ (Linux 5.2-rc7) git grep -En 'strcmp\([^"]*"[[:alnum:]]+"' | wc -l
1968

A quick "strcmp vs strncmp" object size test shows that strcmp()
generates smaller memory footprint (gcc-8, x86_64):

$ (U-Boot) size cmd/bcb-strncmp.o cmd/bcb-strcmp.o
   text	   data	    bss	    dec	    hex	filename
   3373	    400	   2048	   5821	   16bd	cmd/bcb-strncmp.o
   3314	    400	   2048	   5762	   1682	cmd/bcb-strcmp.o

So, overall, I agree to use strcmp() whenever variables are compared
with string literals.
 ----------8<-----------

Fixes: db7b7a05b267 ("cmd: Add 'bcb' command to read/modify/write BCB fields")
Reported-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Reviewed-by: Igor Opaniuk <igor.opaniuk@gmail.com>