alpha: Remove s_ceil{f} and s_floor{f} implementation (BZ#22665)

As discussed in libc-alpha [1], alpha ceil{f} and floor{f}
implementation uses cvttq/svm and although the Alpha Architecture
Handbook version 3 states that that CVTfi OUTPUT Exceptions
(B.3 Mapping to IEEE Standard) should not generate Inexact if INE
bit is set on fpcr, the Alpha 21264 [1] chip manual (A.8 IEEE
Floating-Point Conformance) states that CVTfi and CVTif OUTPUT
does generate inexact exception for inexact result regardless.

As Joseph noted [2] to correctly fix it on alpha we need to either
avoid the instruction or avoid any inexact bit from it being set
on return from the function (while preserving the inexact bit that
might be set on the entry to the function).  The later will result
mf_fpcr followed by a mt_fpcr to get and set the fpcr which will
defeat the optimization itself.

So the patch just remove the alpha optimized and rely on generic
implementation.  It fixes the math/test-*-{ceil,floor} on alpha.

	[BZ #15479]
	[BZ #22665]
	* sysdeps/alpha/fpu/s_ceil.c: Remove file.
	* sysdeps/alpha/fpu/s_ceilf.c: Likewise.
	* sysdeps/alpha/fpu/s_floor.c: Likewise.
	* sysdeps/alpha/fpu/s_floorf.c: Likewise.

[1] https://www.star.bnl.gov/public/daq/HARDWARE/21264_data_sheet.pdf
[2] https://sourceware.org/ml/libc-alpha/2018-01/msg00086.html

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

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