Revert "Change filenames in picolibc test-ungetc-ftell,test-fgets-eof"

This reverts commit ab68577.

picolibc upstream has merged the PR containing the same patch, so
applying an extra copy of it here is no longer necessary, and worse,
causes a conflict.

patches/picolibc.patch

@@ -35,63 +35,3 @@ index b97ea3300..04b94f35c 100644
  		*(.gnu.linkonce.t.*)
  		KEEP (*(.fini .fini.*))
  		@PREFIX@__text_end = .;
-diff --git a/test/test-fgets-eof.c b/test/test-fgets-eof.c
-index 4c9e141b7..704e1a3ac 100644
---- a/test/test-fgets-eof.c
-+++ b/test/test-fgets-eof.c
-@@ -36,6 +36,10 @@
- #include <stdio.h>
- #include <string.h>
-
-+#ifndef TEST_FILE_NAME
-+#define TEST_FILE_NAME "FGETSEOF.TXT"
-+#endif
-+
- const char *string = "123456789";
-
- int main(void)
-@@ -46,12 +50,12 @@ int main(void)
-     FILE *file;
-     int ret = 0;
-
--    file = fopen("testfile.dat", "w");
-+    file = fopen( TEST_FILE_NAME, "w" );
-     if(file == NULL) return 1;
-     fputs(string, file);
-     fclose(file);
-
--    file = fopen( "testfile.dat", "r" );
-+    file = fopen( TEST_FILE_NAME, "r" );
-     if(file == NULL) return 1;
-
-     /*Calling fgets to reach EOF and check on the returned value*/
-diff --git a/test/test-ungetc-ftell.c b/test/test-ungetc-ftell.c
-index 245679814..a3e702312 100644
---- a/test/test-ungetc-ftell.c
-+++ b/test/test-ungetc-ftell.c
-@@ -36,6 +36,10 @@
- #include <stdio.h>
- #include <string.h>
-
-+#ifndef TEST_FILE_NAME
-+#define TEST_FILE_NAME "UNGETCFTELL.DAT"
-+#endif
-+
- const char *str = "This is a string";
-
- int main(void) {
-@@ -44,12 +48,12 @@ int main(void) {
-     char first;
-     long position, start;
-
--    file = fopen( "testfile.dat", "wb" );
-+    file = fopen( TEST_FILE_NAME, "wb" );
-     if( file == NULL ) return 1;
-     fputs(str, file);
-     fclose(file);
-
--    file = fopen( "testfile.dat", "rb" );
-+    file = fopen( TEST_FILE_NAME, "rb" );
-     if(file == NULL) return 1;
-
-     first = fgetc(file);