grub,grub-efi: Remove -mfpmath=sse on x86

grub,grub-efi: Remove -mfpmath=sse on x86

This option fails with clang compiler when testing for soft-float because
OE enforces this option via CCARGS however, gtub's
makefile/configure does disable all sse options when checking for
soft-float support, but it can not disable -mfpmath=sse as its inserted
by OE, therefore remove it in recipe

Fixes build errors seen with clang/musl like on x86
error: the 'sse' unit is not supported with this instruction set

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>