Fix 'A' operand modifier: PR inline-asm/94095

Fix 'A' operand modifier: PR inline-asm/94095

The problem here is there was a typo in the documentation
for the 'A' modifier in the table, it was recorded as 'a'
in the table on the modifier column.

Committed as obvious.

2020-03-09  Andrew Pinski  <apinski@marvell.com>

	PR inline-asm/94095
	* doc/extend.texi (x86 Operand Modifiers): Fix column
	for 'A' modifier.