bcm53xx: 6.6: fix ASM cache workaround linking

bcm53xx: 6.6: fix ASM cache workaround linking

Kernel 6.6 checks for orphan sections and prints a warning about them,
which in turn will make CI fails as we have Werror enabled there.

Issue is that cache-v7-min.S produces .init.text section which is an
orphan section since it is not being handled by the vmlinux.lds.S linker
script.

So, lets put the generated .init.text section under .text.

Fixes: f0d8ce4f482c ("bcm53xx: add testing support for kernel 6.6")
Signed-off-by: Robert Marko <robimarko@gmail.com>