i386: Fix up TARGET_QIMODE_MATH for many AMD CPU tunings [PR98957]

i386: Fix up TARGET_QIMODE_MATH for many AMD CPU tunings [PR98957]

As written in the PR, TARGET_QIMODE_MATH was meant to be set for all
tunings and it was the case for GCC <= 7, but as the number of
PROCESSOR_* enumerators grew, some AMD tunings (which are at the end
of the list) over time got enumerators with values >= 32 and
TARGET_QIMODE_MATH became disabled for them, in GCC 8 for 2
tunings, in GCC 9 for 7 tunings, in GCC 10 for 8 tunings, and
on the trunk for 11 tunings.

The following patch fixes it by using uhwis rather than uints
and gives them also symbolic names.

2021-02-05  Jakub Jelinek  <jakub@redhat.com>

	PR target/98957
	* config/i386/i386-options.c (m_NONE, m_ALL): Define.
	* config/i386/x86-tune.def (X86_TUNE_BRANCH_PREDICTION_HINTS,
	X86_TUNE_PROMOTE_QI_REGS): Use m_NONE instead of 0U.
	(X86_TUNE_QIMODE_MATH): Use m_ALL instead of ~0U.