The function close_fd_get_file is explicitly a variant of
__close_fd[1].  Now that __close_fd has been renamed close_fd, rename
close_fd_get_file to be consistent with close_fd.

When __alloc_fd, __close_fd and __fd_install were introduced the
double underscore indicated that the function took a struct
files_struct parameter.  The function __close_fd_get_file never has so
the naming has always been inconsistent.  This just cleans things up
so there are not any lingering mentions or references __close_fd left
in the code.

[1] 80cd7956 ("binder: fix use-after-free due to ksys_close() during fdget()")
Link: https://lkml.kernel.org/r/20201120231441.29911-23-ebiederm@xmission.comSigned-off-by: NEric W. Biederman <ebiederm@xmission.com>