x86: Don't pad .tfloat directive output

.tfloat output should always be 10 bytes without padding, independent
of psABIs.  In glibc, x86 assembly codes expect 10-byte .tfloat output.
This also reduces .ds.x output and .tfloat output with hex input from
12 bytes to 10 bytes to match .tfloat output.

	PR gas/28230
	* NEWS: Mention changes of .ds.x output and .tfloat output with
	hex input.
	* config/tc-i386.c (x86_tfloat_pad): Removed.
	* config/tc-i386.h (X_PRECISION_PAD): Changed to 0.
	(x86_tfloat_pad): Removed.
	* testsuite/gas/i386/fp.s: If NO_TFLOAT_PADDING isn't defined,
	add explicit paddings after .tfloat, .ds.x, .dc.x and .dcb.x
	directives.
	* testsuite/gas/i386/i386.exp (ASFLAGS): Append
	"--defsym NO_TFLOAT_PADDING=1" when running the fp test.