[mips] [IAS] Refactor the emitDirectiveModuleFP() functions. NFC.

Summary:
Simplify emitDirectiveModuleFP() by having it just print the current information
from MipsABIFlagsSection and doing an updateABIInfo() before such calls.

This prevents us from forgetting to update the STI.FeatureBits,
because updateABIInfo() uses those to update the MipsABIFlagsSection object,
and also makes sure we use the update mechanism from MipsABIFlagsSection.

Reviewers: dsanders

Reviewed By: dsanders

Subscribers: llvm-commits, mpf

Differential Revision: http://reviews.llvm.org/D10642

llvm-svn: 240637